htoprs 0.3.0

//! Partial port of `linux/LinuxProcessTable.c` — the Linux `/proc` process
//! scanner and its `LinuxProcessTable` container.
//!
//! Ported: the fast integer parsers (`fast_strto*`), `strtopid`,
//! `sortTtyDrivers`, `LinuxProcessTable_getProcessState`,
//! `LinuxProcessTable_adjustTime`, `fopenat`, `LinuxProcessTable_initTtyDrivers`,
//! `ProcessTable_new`, `readFileDynamic`, `isOlderThan`, and the per-process
//! `/proc` file readers that only need already-ported substrate:
//! `readStatFile`, `readStatusFile`, `readStatmFile`, `readOomData`,
//! `readAutogroup`, `readCwd`, `readIoFile`, `readCGroupFile`,
//! `readSecattrData`, `LinuxProcessList_readExe`,
//! `LinuxProcessTable_readCmdlineFile`, `LinuxProcessList_readComm`.
//!
//! Still stubbed (each fn's doc gives the precise blocker): the scan drivers
//! `LinuxProcessTable_recurseProcTree` / `ProcessTable_goThroughEntries`
//! (need the process-typed `ProcessTable_getProcess`/`_add`, still stubbed in
//! `processtable.rs`); `updateUser` (opaque `usersTable`); `readMaps` +
//! `calcLibSize_helper` (`Hashtable` is ported, but `Hashtable_get` is
//! immutable so the in-place `libdata->size` aggregate can't be updated, and
//! `LibraryData` isn't modeled as an `Object`); `readSmapsFile`
//! (`skipEndOfLine` unported); `updateTtyDevice` (`major`/`minor` macros
//! unported); `ProcessTable_delete` (pure `free()` teardown → `Drop`); and
//! `readOpenVZData` (`#ifdef HAVE_OPENVZ` reader needing `skipEndOfLine` +
//! unmodeled `ctid`/`vpid` fields).
#![allow(non_snake_case)]
#![allow(dead_code)]

use core::ffi::CStr;
use std::os::unix::io::FromRawFd;
use std::sync::atomic::{AtomicU64, Ordering};

use libc::ssize_t;

use crate::ported::linux::cgrouputils::{CGroup_filterContainer, CGroup_filterName};
use crate::ported::linux::compat::{
    openat_arg_t, Compat_faccessat, Compat_openat, Compat_readfile, Compat_readfileat,
};
use crate::ported::linux::linuxmachine::LinuxMachine;
use crate::ported::linux::linuxprocess::LinuxProcess;
use crate::ported::machine::Machine;
use crate::ported::process::{
    Process, ProcessField, ProcessState, Process_getPid, Process_setParent, Process_updateCmdline,
    Process_updateComm, Process_updateExe, Tristate,
};
use crate::ported::processtable::{ProcessTable, ProcessTable_init};
use crate::ported::row::{spaceship_number, Row_updateFieldWidth};
use crate::ported::settings::RowField;
use crate::ported::xutils::{
    saturatingSub, String_eq, String_safeStrncpy, String_startsWith, String_strchrnul,
};

/// Port of `#define PROCDIR "/proc"` (`LinuxMachine.h:105`).
const PROCDIR: &str = "/proc";
/// Port of `#define PROCTTYDRIVERSFILE PROCDIR "/tty/drivers"`
/// (`LinuxMachine.h:125`).
const PROCTTYDRIVERSFILE: &CStr = c"/proc/tty/drivers";
/// Port of `#define PROC_LINE_LENGTH 4096` (`LinuxMachine.h:129`).
const PROC_LINE_LENGTH: usize = 4096;
/// Port of `#define MAX_READ 2048` (`Machine.h:32`).
const MAX_READ: usize = 2048;
/// Port of `#define MAX_NAME 128` (`Machine.h:28`).
const MAX_NAME: usize = 128;
/// Port of `PATH_MAX` (`Compat.c:24` / `limits.h`; 4096 on Linux).
const PATH_MAX: usize = 4096;
/// Port of `#define PF_KTHREAD 0x00200000` (`LinuxProcessTable.c:61`).
const PF_KTHREAD: u64 = 0x0020_0000;
/// Port of `#define MAX_CMDLINE_BUFFER_SIZE (2 * 1024 * 1024 + 512)`
/// (`LinuxProcessTable.c:65`).
const MAX_CMDLINE_BUFFER_SIZE: usize = 2 * 1024 * 1024 + 512;

/// Port of `static ino_t rootPidNs = (ino_t)-1;` (`LinuxProcessTable.c:68`),
/// the inode number of htop's own PID namespace. The C `(ino_t)-1` sentinel
/// is modeled as `u64::MAX` in an [`AtomicU64`] (a module-private mutable C
/// static; see the `Row_uidDigits` idiom).
#[allow(non_upper_case_globals)] // faithful C identifier `rootPidNs`
static rootPidNs: AtomicU64 = AtomicU64::new(u64::MAX);

/// Port of `struct TtyDriver_` (`LinuxProcessTable.h:15`). One row of
/// `/proc/tty/drivers`, describing a tty driver's major/minor range and
/// the device-node path prefix used to reconstruct a TTY name.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct TtyDriver {
    /// C `char* path` — device-node path prefix (e.g. `/dev/ttyS`).
    /// `None` marks the sentinel terminator entry of the C array.
    pub path: Option<String>,
    /// C `unsigned int major`.
    pub major: u32,
    /// C `unsigned int minorFrom`.
    pub minorFrom: u32,
    /// C `unsigned int minorTo`.
    pub minorTo: u32,
}

/// Port of `struct LinuxProcessTable_` (`LinuxProcessTable.h:22`).
/// "Extends" [`ProcessTable`] via the embedded `super_` field and adds
/// the Linux-specific tty-driver table and capability flags. The
/// `HAVE_DELAYACCT`-gated netlink fields are omitted here — this build
/// commits to the non-delayacct branch (see the `libnl` module).
pub struct LinuxProcessTable {
    /// C `ProcessTable super` — the embedded base table.
    pub super_: ProcessTable,
    /// C `TtyDriver* ttyDrivers` — NUL-path-terminated, major/minor-sorted
    /// array; `None` until `LinuxProcessTable_initTtyDrivers` runs.
    pub ttyDrivers: Option<Vec<TtyDriver>>,
    /// C `bool haveSmapsRollup` — `/proc/self/smaps_rollup` available.
    pub haveSmapsRollup: bool,
    /// C `bool haveAutogroup` — autogroup scheduling supported.
    pub haveAutogroup: bool,
}

/// Port of `LinuxProcessTable.c:71`. Opens `pathname` (relative to the
/// directory handle `openatArg`) via [`Compat_openat`] and wraps the fd in a
/// buffered file handle. The C `FILE*` is modeled as an owned
/// [`std::fs::File`] (the `TraceScreen`/`OpenFilesScreen` idiom); `None`
/// mirrors the C `NULL` return. Only `mode == "r"` is supported, matching the
/// C `assert(String_eq(mode, "r"))`. `File::from_raw_fd` cannot fail, so the
/// C `fdopen` NULL branch (`close(fd)`) is unreachable.
fn fopenat(openatArg: openat_arg_t, pathname: &CStr, mode: &str) -> Option<std::fs::File> {
    debug_assert!(mode == "r"); // only currently supported mode

    let fd = Compat_openat(openatArg, pathname, libc::O_RDONLY);
    if fd < 0 {
        return None;
    }

    Some(unsafe { std::fs::File::from_raw_fd(fd) })
}

/// Port of `LinuxProcessTable.c:85`. Parse a `/proc` directory name into
/// a pid, returning `0` (an invalid pid) on failure. Mirrors the C
/// `strtoul(str, &endptr, 10)` semantics: leading whitespace and an
/// optional sign are consumed, the whole remaining string must be
/// digits, and the value must be in `1 ..< INT_MAX`.
pub fn strtopid(str: &str) -> i32 {
    let bytes = str.as_bytes();
    let mut i = 0;

    // strtoul() skips leading whitespace.
    while i < bytes.len() && bytes[i].is_ascii_whitespace() {
        i += 1;
    }

    // strtoul() accepts an optional leading sign.
    let mut neg = false;
    if i < bytes.len() && (bytes[i] == b'+' || bytes[i] == b'-') {
        neg = bytes[i] == b'-';
        i += 1;
    }

    let mut parsed: u64 = 0;
    while i < bytes.len() && bytes[i].is_ascii_digit() {
        parsed = parsed
            .wrapping_mul(10)
            .wrapping_add((bytes[i] - b'0') as u64);
        i += 1;
    }

    // *endptr != '\0' — trailing characters remain unconsumed.
    let endptr_is_nul = i == bytes.len();
    let parsed_pid = if neg { parsed.wrapping_neg() } else { parsed };

    if parsed_pid == 0 || parsed_pid >= i32::MAX as u64 || !endptr_is_nul {
        return 0; // indicate failure by an invalid pid
    }

    parsed_pid as i32
}

/// Port of `LinuxProcessTable.c:93`. Parse an unsigned decimal integer
/// from the front of `str`, advancing the cursor past the digits it
/// consumes. `maxlen == 0` means "no explicit cap" (defaults to 20, the
/// digit count of `u64::MAX`). The C `char**` cursor is modeled as a
/// `&mut &[u8]` byte slice; end-of-string (empty slice) reads as the NUL
/// terminator, which is not a digit and stops the loop.
pub fn fast_strtoull_dec(str: &mut &[u8], mut maxlen: usize) -> u64 {
    let mut result: u64 = 0;

    if maxlen == 0 {
        maxlen = 20; // length of maximum value of 18446744073709551615
    }

    while maxlen > 0 {
        match str.first() {
            Some(&c) if c.is_ascii_digit() => {
                result = result.wrapping_mul(10);
                result = result.wrapping_add((c - b'0') as u64);
                *str = &str[1..];
            }
            _ => break,
        }
        maxlen -= 1;
    }

    result
}

/// Port of `LinuxProcessTable.c:108`. Signed decimal variant of
/// [`fast_strtoull_dec`]: consumes an optional leading `-`, then the
/// magnitude, and negates as needed.
pub fn fast_strtoll_dec(str: &mut &[u8], maxlen: usize) -> i64 {
    let mut neg = false;

    if str.first() == Some(&b'-') {
        neg = true;
        *str = &str[1..];
    }

    let res = fast_strtoull_dec(str, maxlen);
    debug_assert!(res <= i64::MAX as u64);
    let result = res as i64;

    if neg {
        -result
    } else {
        result
    }
}

/// Port of `LinuxProcessTable.c:123`. `int` decimal variant of
/// [`fast_strtoll_dec`]; `maxlen == 0` defaults to 10 (digit count of
/// `i32::MAX`).
pub fn fast_strtoi_dec(str: &mut &[u8], mut maxlen: usize) -> i32 {
    if maxlen == 0 {
        maxlen = 10; // length of maximum value of 2147483647
    }
    let result = fast_strtoll_dec(str, maxlen);
    debug_assert!(result <= i32::MAX as i64);
    debug_assert!(result >= i32::MIN as i64);
    result as i32
}

/// Port of `LinuxProcessTable.c:132`. `long` decimal variant of
/// [`fast_strtoll_dec`]. On this (LP64) target `long` is 64-bit, so the
/// C `LONG_MIN`/`LONG_MAX` bounds asserts are tautological.
pub fn fast_strtol_dec(str: &mut &[u8], maxlen: usize) -> i64 {
    fast_strtoll_dec(str, maxlen)
}

/// Port of `LinuxProcessTable.c:139`. `unsigned long` decimal variant of
/// [`fast_strtoull_dec`]. On this (LP64) target `unsigned long` is
/// 64-bit, so the C `ULONG_MAX` bounds assert is tautological.
pub fn fast_strtoul_dec(str: &mut &[u8], maxlen: usize) -> u64 {
    fast_strtoull_dec(str, maxlen)
}

/// Port of `LinuxProcessTable.c:145`. Parse an unsigned hexadecimal
/// integer from the front of `str`, advancing the cursor. `maxlen == 0`
/// defaults to 18 (digit count of `0xffffffffffffffff`). Faithful to the
/// C bit-twiddling nibble decoder: `valid_mask` gates on the low 5 bits
/// of the byte, then the byte is folded to upper case and mapped to its
/// 0–15 nibble value.
pub fn fast_strtoull_hex(str: &mut &[u8], mut maxlen: usize) -> u64 {
    let mut result: u64 = 0;
    let valid_mask: i64 = 0x03FF007E;

    if maxlen == 0 {
        maxlen = 18; // length of maximum value of 0xffffffffffffffff
    }

    while maxlen > 0 {
        maxlen -= 1;

        // (unsigned char)**str — end-of-string reads as NUL (0).
        let mut nibble: i32 = match str.first() {
            Some(&c) => c as i32,
            None => 0,
        };

        if (valid_mask & (1i64 << (nibble & 0x1F))) == 0 {
            break;
        }
        if nibble < b'0' as i32 || (nibble & !0x20) > b'F' as i32 {
            break;
        }
        let letter = if (nibble & 0x40) != 0 {
            b'A' as i32 - b'9' as i32 - 1
        } else {
            0
        };
        nibble &= !0x20; // to upper
        nibble ^= 0x10; // switch letters and digits
        nibble -= letter;
        nibble &= 0x0f;
        result <<= 4;
        result += nibble as u64;
        *str = &str[1..];
    }

    result
}

/// Port of `LinuxProcessTable.c:172`. `qsort` comparator ordering
/// [`TtyDriver`] entries by `major`, then `minorFrom`. Returns the C
/// three-way `-1`/`0`/`1` result.
pub fn sortTtyDrivers(va: &TtyDriver, vb: &TtyDriver) -> i32 {
    let a = va;
    let b = vb;

    let r = spaceship_number!(a.major, b.major);
    if r != 0 {
        return r;
    }

    spaceship_number!(a.minorFrom, b.minorFrom)
}

/// Port of `LinuxProcessTable.c:183`. Reads and parses `/proc/tty/drivers`
/// into the major/minor-sorted [`TtyDriver`] table stored on `this`. Each
/// line has the form `name  nodepath  major  minor-range  type`. The C
/// in-place `strchr`/`atoi` tokenizer is expressed here with line/whitespace
/// splitting yielding the same fields; a partial (truncated) final line is
/// dropped, matching the C `goto finish` bail-outs. The trailing
/// `path == NULL` sentinel the C array carries is modeled as a final
/// [`TtyDriver`] with `path: None`.
fn LinuxProcessTable_initTtyDrivers(this: &mut LinuxProcessTable) {
    let mut buf = [0u8; 16384];
    let r = Compat_readfile(PROCTTYDRIVERSFILE, &mut buf);
    if r < 0 {
        return;
    }

    // atoi(): parse the leading run of decimal digits, defaulting to 0.
    let atoi = |s: &str| -> u32 {
        let mut v: u32 = 0;
        for c in s.bytes() {
            if !c.is_ascii_digit() {
                break;
            }
            v = v.wrapping_mul(10).wrapping_add((c - b'0') as u32);
        }
        v
    };

    let text = &buf[..r as usize];
    let mut ttyDrivers: Vec<TtyDriver> = Vec::new();

    for line in text.split(|&c| c == b'\n') {
        // [name]  [node path]  [major]  [minor range]  [type]
        let line = match std::str::from_utf8(line) {
            Ok(s) => s,
            Err(_) => continue,
        };
        let mut it = line.split_whitespace();

        // skip first token (name)
        if it.next().is_none() {
            continue;
        }
        let path = match it.next() {
            Some(p) => p,
            None => continue, // truncation
        };
        let major = match it.next() {
            Some(m) => atoi(m),
            None => continue, // truncation
        };
        let minor = match it.next() {
            Some(m) => m,
            None => continue, // truncation
        };

        let (minorFrom, minorTo) = match minor.split_once('-') {
            Some((from, to)) => (atoi(from), atoi(to)),
            None => (atoi(minor), atoi(minor)),
        };

        ttyDrivers.push(TtyDriver {
            path: Some(path.to_string()),
            major,
            minorFrom,
            minorTo,
        });
    }

    // qsort(ttyDrivers, numDrivers, ...): sort the real entries only.
    ttyDrivers.sort_by(|a, b| match sortTtyDrivers(a, b) {
        n if n < 0 => std::cmp::Ordering::Less,
        0 => std::cmp::Ordering::Equal,
        _ => std::cmp::Ordering::Greater,
    });

    // ttyDrivers[numDrivers].path = NULL; — the sentinel terminator.
    ttyDrivers.push(TtyDriver::default());

    this.ttyDrivers = Some(ttyDrivers);
}

/// Port of `LinuxProcessTable.c:261`. Constructs the Linux process table:
/// initializes the embedded base [`ProcessTable`], loads the tty-driver
/// table, probes `/proc/self/smaps_rollup` availability, and records htop's
/// own PID-namespace inode in the `rootPidNs` static.
///
/// Signature mapping: the C `xCalloc` + `Object_setClass` heap allocation is
/// modeled as an owned [`LinuxProcessTable`] value (the `LinuxProcess_new`
/// idiom); class identity is the Rust type. The C returns `&this->super`
/// (a `ProcessTable*` upcast); the owning caller here keeps the concrete
/// value. `Hashtable* pidMatchList` is the opaque [`Option<usize>`] handle.
pub fn ProcessTable_new(host: *const Machine, pidMatchList: Option<usize>) -> LinuxProcessTable {
    let mut this = LinuxProcessTable {
        super_: ProcessTable::empty(),
        ttyDrivers: None,
        haveSmapsRollup: false,
        haveAutogroup: false,
    };

    ProcessTable_init(&mut this.super_, host, pidMatchList);

    LinuxProcessTable_initTtyDrivers(&mut this);

    // Test /proc/PID/smaps_rollup availability (faster to parse, Linux 4.14+)
    this.haveSmapsRollup =
        unsafe { libc::access(c"/proc/self/smaps_rollup".as_ptr(), libc::R_OK) } == 0;

    // Read PID namespace inode number
    let mut sb: libc::stat = unsafe { std::mem::zeroed() };
    let r = unsafe { libc::stat(c"/proc/self/ns/pid".as_ptr(), &mut sb) };
    if r == 0 {
        rootPidNs.store(sb.st_ino as u64, Ordering::Relaxed);
    } else {
        rootPidNs.store(u64::MAX, Ordering::Relaxed);
    }

    this
}

/// TODO: port of `void ProcessTable_delete(Object* cast)` from
/// `LinuxProcessTable.c:287`. Kept stubbed: a pure `free()` teardown —
/// `ProcessTable_done(&this->super)`, then `free()` of each `ttyDrivers[i].path`
/// and the array, the `#ifdef HAVE_DELAYACCT` netlink-socket destroy (the
/// non-delayacct build variant this module commits to omits it), and
/// `free(this)`. Rust owns the `Option<Vec<TtyDriver>>` and every
/// `Option<String>`, so `Drop` reclaims them automatically (the
/// `Affinity_delete` precedent).
pub fn ProcessTable_delete() {
    todo!("port of LinuxProcessTable.c:287 — pure free() teardown; Rust Drop handles it")
}

/// Port of `LinuxProcessTable.c:302`. Rescales a jiffy-denominated time `t`
/// to hundredths of a second using the host's `USER_HZ` (`jiffies`).
fn LinuxProcessTable_adjustTime(lhost: &LinuxMachine, t: u64) -> u64 {
    t * 100 / lhost.jiffies as u64
}

/// Port of `LinuxProcessTable.c:307`. Map the single-character process
/// state from `/proc/<pid>/stat` to a [`ProcessState`]. Taken from the
/// Linux kernel `fs/proc/array.c` state table.
pub fn LinuxProcessTable_getProcessState(state: u8) -> ProcessState {
    match state {
        b'S' => ProcessState::SLEEPING,
        b'X' => ProcessState::DEFUNCT,
        b'Z' => ProcessState::ZOMBIE,
        b't' => ProcessState::TRACED,
        b'T' => ProcessState::STOPPED,
        b'D' => ProcessState::UNINTERRUPTIBLE_WAIT,
        b'R' => ProcessState::RUNNING,
        b'P' => ProcessState::BLOCKED,
        b'I' => ProcessState::IDLE,
        _ => ProcessState::UNKNOWN,
    }
}

/// Port of `LinuxProcessTable.c:325`. Reads and parses `/proc/<pid>/stat`
/// (thread-specific data) into the [`LinuxProcess`]/[`Process`] fields,
/// copying the parenthesized `comm` into `command`. The C `char* location`
/// cursor is modeled as a byte index `loc` into the NUL-terminated read
/// buffer (out-of-range / past-NUL reads model as `0`); each field is read
/// via the `fast_strto*` helpers (which advance a `&mut &[u8]` suffix of the
/// buffer). `commLen` caps the `comm` copy exactly as the C `MINIMUM(...)`.
fn LinuxProcessTable_readStatFile(
    lp: &mut LinuxProcess,
    procFd: openat_arg_t,
    lhost: &LinuxMachine,
    scanMainThread: bool,
    command: &mut [u8],
    commLen: usize,
) -> bool {
    let mut buf = [0u8; MAX_READ + 1];

    // char path[22] = "stat"; task/<pid>/stat when scanning the main thread.
    let path = if scanMainThread {
        std::ffi::CString::new(format!("task/{}/stat", Process_getPid(&lp.super_))).unwrap()
    } else {
        std::ffi::CString::new("stat").unwrap()
    };
    let r = Compat_readfileat(procFd, &path, &mut buf);
    if r < 0 {
        return false;
    }

    // Byte at `i`, with past-end / NUL-region reads as 0 (NUL terminator).
    let byte = |i: usize| -> u8 { buf.get(i).copied().unwrap_or(0) };
    // strchr(&buf[from], ch): first index >= from holding ch before the NUL.
    let find = |from: usize, ch: u8| -> Option<usize> {
        let mut i = from;
        loop {
            let c = buf.get(i).copied().unwrap_or(0);
            if c == 0 {
                return None;
            }
            if c == ch {
                return Some(i);
            }
            i += 1;
        }
    };
    // fast_strto* helpers over the buffer suffix at `loc`, returning the new
    // cursor index alongside the value.
    let read_i = |loc: usize| -> (i32, usize) {
        let mut cur: &[u8] = &buf[loc..];
        let v = fast_strtoi_dec(&mut cur, 0);
        (v, buf.len() - cur.len())
    };
    let read_ul = |loc: usize| -> (u64, usize) {
        let mut cur: &[u8] = &buf[loc..];
        let v = fast_strtoul_dec(&mut cur, 0);
        (v, buf.len() - cur.len())
    };
    let read_ull = |loc: usize| -> (u64, usize) {
        let mut cur: &[u8] = &buf[loc..];
        let v = fast_strtoull_dec(&mut cur, 0);
        (v, buf.len() - cur.len())
    };
    let read_l = |loc: usize| -> (i64, usize) {
        let mut cur: &[u8] = &buf[loc..];
        let v = fast_strtol_dec(&mut cur, 0);
        (v, buf.len() - cur.len())
    };
    let read_ll = |loc: usize| -> (i64, usize) {
        let mut cur: &[u8] = &buf[loc..];
        let v = fast_strtoll_dec(&mut cur, 0);
        (v, buf.len() - cur.len())
    };

    /* (1) pid   -  %d */
    debug_assert_eq!(
        Process_getPid(&lp.super_),
        fast_strtoi_dec(&mut &buf[..], 0)
    );
    let mut loc = match find(0, b' ') {
        Some(i) => i,
        None => return false,
    };

    /* (2) comm  -  (%s) */
    if byte(loc) == 0 || byte(loc + 1) == 0 {
        return false;
    }
    loc += 2;
    // strrchr(location, ')')
    let end = {
        let mut e: Option<usize> = None;
        let mut i = loc;
        while byte(i) != 0 {
            if byte(i) == b')' {
                e = Some(i);
            }
            i += 1;
        }
        match e {
            Some(i) => i,
            None => return false,
        }
    };
    if end < loc {
        return false;
    }
    let size = core::cmp::min(end - loc + 1, commLen).min(command.len());
    if size > 0 {
        String_safeStrncpy(&mut command[..size], &buf[loc..]);
    }
    if byte(end) == 0 || byte(end + 1) == 0 {
        return false;
    }
    loc = end + 2;

    /* (3) state  -  %c */
    lp.super_.state = LinuxProcessTable_getProcessState(byte(loc));
    if byte(loc) == 0 || byte(loc + 1) == 0 {
        return false;
    }
    loc += 2;

    /* (4) ppid  -  %d */
    let (ppid, l) = read_i(loc);
    Process_setParent(&mut lp.super_, ppid);
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (5) pgrp  -  %d */
    let (v, l) = read_i(loc);
    lp.super_.pgrp = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (6) session  -  %d */
    let (v, l) = read_i(loc);
    lp.super_.session = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (7) tty_nr  -  %d */
    let (v, l) = read_ul(loc);
    lp.super_.tty_nr = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (8) tpgid  -  %d */
    let (v, l) = read_i(loc);
    lp.super_.tpgid = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (9) flags  -  %u */
    let (v, l) = read_ul(loc);
    lp.flags = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (10) minflt  -  %lu */
    let (v, l) = read_ull(loc);
    lp.super_.minflt = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (11) cminflt  -  %lu */
    let (v, l) = read_ull(loc);
    lp.cminflt = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (12) majflt  -  %lu */
    let (v, l) = read_ull(loc);
    lp.super_.majflt = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (13) cmajflt  -  %lu */
    let (v, l) = read_ull(loc);
    lp.cmajflt = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (14) utime  -  %lu */
    let (v, l) = read_ull(loc);
    lp.utime = LinuxProcessTable_adjustTime(lhost, v);
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (15) stime  -  %lu */
    let (v, l) = read_ull(loc);
    lp.stime = LinuxProcessTable_adjustTime(lhost, v);
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (16) cutime  -  %ld */
    let (v, l) = read_ull(loc);
    lp.cutime = LinuxProcessTable_adjustTime(lhost, v);
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (17) cstime  -  %ld */
    let (v, l) = read_ull(loc);
    lp.cstime = LinuxProcessTable_adjustTime(lhost, v);
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (18) priority  -  %ld */
    let (v, l) = read_l(loc);
    lp.super_.priority = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (19) nice  -  %ld */
    let (v, l) = read_i(loc);
    lp.super_.nice = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* (20) num_threads  -  %ld */
    let (v, l) = read_l(loc);
    lp.super_.nlwp = v;
    loc = l;
    if byte(loc) == 0 {
        return false;
    }
    loc += 1;

    /* Skip (21) itrealvalue  -  %ld */
    loc = match find(loc, b' ') {
        Some(i) => i,
        None => return false,
    };
    loc += 1;

    /* (22) starttime  -  %llu */
    if lp.super_.starttime_ctime == 0 {
        let (v, l) = read_ll(loc);
        lp.super_.starttime_ctime =
            lhost.boottime + (LinuxProcessTable_adjustTime(lhost, v as u64) / 100) as i64;
        loc = l;
    } else {
        loc = match find(loc, b' ') {
            Some(i) => i,
            None => return false,
        };
    }
    loc += 1;

    /* Skip (23) - (38) */
    for _ in 0..16 {
        loc = match find(loc, b' ') {
            Some(i) => i,
            None => return false,
        };
        loc += 1;
    }

    /* (39) processor  -  %d */
    let (v, _l) = read_i(loc);
    lp.super_.processor = v;

    /* Ignore further fields */

    lp.super_.time = lp.utime + lp.stime;

    true
}

/// Port of `LinuxProcessTable.c:549`. Reads `/proc/<pid>/status`, detecting
/// container membership (the `NSpid:` line listing more than one pid
/// namespace) and summing the voluntary + nonvoluntary context switches into
/// the [`LinuxProcess`] `ctxt_total`/`ctxt_diff` counters. The C `fgets`
/// line loop over a `FILE*` opened by [`fopenat`] becomes a buffered
/// line iterator; `sscanf(..., "\t%lu")` becomes a strip-prefix + trim +
/// parse.
///
/// Signature mapping: the C takes `Process*` and immediately downcasts to
/// `LinuxProcess*`; the faithful Rust receiver is the concrete
/// `&mut LinuxProcess`, reaching the base via `super_`.
fn LinuxProcessTable_readStatusFile(process: &mut LinuxProcess, procFd: openat_arg_t) -> bool {
    use std::io::BufRead;

    let mut ctxt: u64 = 0;
    process.super_.isRunningInContainer = Tristate::TRI_OFF;

    let statusfile = match fopenat(procFd, c"status", "r") {
        Some(f) => f,
        None => return false,
    };

    let reader = std::io::BufReader::new(statusfile);
    for line in reader.lines() {
        let buffer = match line {
            Ok(l) => l,
            Err(_) => break,
        };

        if String_startsWith(&buffer, "NSpid:") {
            // Count the distinct numeric fields (each a pid in one namespace).
            let bytes = buffer.as_bytes();
            let mut pid_ns_count = 0;
            let mut i = 0;
            while i < bytes.len() && !bytes[i].is_ascii_digit() {
                i += 1;
            }
            while i < bytes.len() {
                if bytes[i].is_ascii_digit() {
                    pid_ns_count += 1;
                    while i < bytes.len() && bytes[i].is_ascii_digit() {
                        i += 1;
                    }
                }
                while i < bytes.len() && !bytes[i].is_ascii_digit() {
                    i += 1;
                }
            }

            if pid_ns_count > 1 {
                process.super_.isRunningInContainer = Tristate::TRI_ON;
            }
        } else if String_startsWith(&buffer, "voluntary_ctxt_switches:") {
            if let Some(v) = buffer
                .strip_prefix("voluntary_ctxt_switches:")
                .and_then(|s| s.trim().parse::<u64>().ok())
            {
                ctxt += v;
            }
        } else if String_startsWith(&buffer, "nonvoluntary_ctxt_switches:") {
            if let Some(v) = buffer
                .strip_prefix("nonvoluntary_ctxt_switches:")
                .and_then(|s| s.trim().parse::<u64>().ok())
            {
                ctxt += v;
            }
        }
    }

    process.ctxt_diff = if ctxt > process.ctxt_total {
        ctxt - process.ctxt_total
    } else {
        0
    };
    process.ctxt_total = ctxt;

    true
}

/// TODO: port of `static bool LinuxProcessTable_updateUser(const Machine*
/// host, Process* process, openat_arg_t procFd, const LinuxProcess* mainTask)`
/// from `LinuxProcessTable.c:628`. Blocked: the non-`mainTask` path calls
/// `UsersTable_getRef(host->usersTable, sb.st_uid)` to resolve the username,
/// but [`Machine::usersTable`](crate::ported::machine::Machine) is the opaque
/// `Option<usize>` handle (the `UsersTable` is not modeled as a reachable
/// value), so the ported `UsersTable_getRef` (which needs `&mut UsersTable`)
/// cannot be called. Stays stubbed until the machine exposes a real
/// `UsersTable`.
pub fn LinuxProcessTable_updateUser() {
    todo!("port of LinuxProcessTable.c:628 — needs Machine::usersTable as a real UsersTable")
}

/// Port of `static void LinuxProcessTable_readIoFile(LinuxProcess* lp,
/// openat_arg_t procFd, bool scanMainThread)` from `LinuxProcessTable.c:655`.
/// Reads `/proc/<pid>/io` (or `task/<tid>/io` when `scanMainThread`) and
/// updates the per-process IO counters and derived read/write byte rates.
/// A read failure resets every counter to its "unknown" sentinel
/// (`ULLONG_MAX` / `NAN`) and records the scan time. Otherwise the
/// `strsep(&buf, "\n")` line loop is reproduced with [`str::split`], and the
/// per-field prefixes (`rchar: `/`wchar: `/`read_bytes: `/`write_bytes: `/
/// `syscr: `/`syscw: `/`cancelled_write_bytes: `) are matched with
/// [`str::strip_prefix`], mirroring the C `line[i]` guards + `String_startsWith`.
/// The rates use [`saturatingSub`] on the byte and time deltas (`ms → s`),
/// yielding `NAN` when `time_delta == 0`, exactly as the C.
///
/// The C derives `host` from `process->super.super.host`; the ported reader
/// takes it as an explicit `&LinuxMachine` param (the [`LinuxProcessTable_readStatmFile`]
/// convention), reading `realtimeMs` from `host.super_`.
///
/// `strtoull(ptr, NULL, 10)` is the local `strtoull` closure: it skips leading
/// whitespace and an optional sign, then accumulates decimal digits saturating
/// at [`u64::MAX`] (C's `ULLONG_MAX`), matching `strtoull`'s overflow clamp.
fn LinuxProcessTable_readIoFile(
    lp: &mut LinuxProcess,
    procFd: openat_arg_t,
    host: &LinuxMachine,
    scanMainThread: bool,
) {
    let realtimeMs = host.super_.realtimeMs;

    // char path[20] = "io"; if (scanMainThread) snprintf "task/<pid>/io".
    let path = if scanMainThread {
        std::ffi::CString::new(format!("task/{}/io", Process_getPid(&lp.super_))).unwrap()
    } else {
        std::ffi::CString::new("io").unwrap()
    };

    let mut buffer = [0u8; 1024];
    let r = Compat_readfileat(procFd, &path, &mut buffer);
    if r < 0 {
        lp.io_rate_read_bps = f64::NAN;
        lp.io_rate_write_bps = f64::NAN;
        lp.io_rchar = u64::MAX;
        lp.io_wchar = u64::MAX;
        lp.io_syscr = u64::MAX;
        lp.io_syscw = u64::MAX;
        lp.io_read_bytes = u64::MAX;
        lp.io_write_bytes = u64::MAX;
        lp.io_cancelled_write_bytes = u64::MAX;
        lp.io_last_scan_time_ms = realtimeMs;
        return;
    }

    let last_read = lp.io_read_bytes;
    let last_write = lp.io_write_bytes;
    let time_delta = saturatingSub(realtimeMs, lp.io_last_scan_time_ms);

    // strtoull(s, NULL, 10): skip whitespace + optional sign, saturate at u64::MAX.
    let strtoull = |s: &str| -> u64 {
        let b = s.as_bytes();
        let mut i = 0;
        while i < b.len() && b[i].is_ascii_whitespace() {
            i += 1;
        }
        if i < b.len() && (b[i] == b'+' || b[i] == b'-') {
            i += 1;
        }
        let mut v: u64 = 0;
        while i < b.len() && b[i].is_ascii_digit() {
            v = v.saturating_mul(10).saturating_add((b[i] - b'0') as u64);
            i += 1;
        }
        v
    };

    let text = std::str::from_utf8(&buffer[..r as usize]).unwrap_or("");
    for line in text.split('\n') {
        // C switches on line[0], then String_startsWith on the remainder.
        if let Some(rest) = line.strip_prefix("rchar: ") {
            lp.io_rchar = strtoull(rest);
        } else if let Some(rest) = line.strip_prefix("read_bytes: ") {
            lp.io_read_bytes = strtoull(rest);
            lp.io_rate_read_bps = if time_delta != 0 {
                saturatingSub(lp.io_read_bytes, last_read) as f64 * 1000. / time_delta as f64
            } else {
                f64::NAN
            };
        } else if let Some(rest) = line.strip_prefix("wchar: ") {
            lp.io_wchar = strtoull(rest);
        } else if let Some(rest) = line.strip_prefix("write_bytes: ") {
            lp.io_write_bytes = strtoull(rest);
            lp.io_rate_write_bps = if time_delta != 0 {
                saturatingSub(lp.io_write_bytes, last_write) as f64 * 1000. / time_delta as f64
            } else {
                f64::NAN
            };
        } else if let Some(rest) = line.strip_prefix("syscr: ") {
            lp.io_syscr = strtoull(rest);
        } else if let Some(rest) = line.strip_prefix("syscw: ") {
            lp.io_syscw = strtoull(rest);
        } else if let Some(rest) = line.strip_prefix("cancelled_write_bytes: ") {
            lp.io_cancelled_write_bytes = strtoull(rest);
        }
    }

    lp.io_last_scan_time_ms = realtimeMs;
}

/// TODO: port of `static void LinuxProcessTable_calcLibSize_helper(
/// ATTR_UNUSED ht_key_t key, void* value, void* data)` from
/// `LinuxProcessTable.c:727`. This is a `Hashtable_foreach` callback
/// (`Hashtable_PairFunction`) invoked by [`LinuxProcessTable_readMaps`] over a
/// `Hashtable` of the file-local `LibraryData` (`{ uint64_t size; bool exec }`)
/// type. `Hashtable` itself *is* ported now, but two pieces are still missing:
/// (1) `LibraryData` is not modeled as an [`Object`](crate::ported::object::Object)
/// (the value type the ported `Hashtable` stores), and (2) the ported
/// `Hashtable_foreach` takes a `&mut dyn FnMut(u32, &dyn Object)` closure, so a
/// free-standing `(ht_key_t, void*, void*)` callback has no matching slot —
/// it is expressed as the closure body inside `readMaps` instead. Stays
/// stubbed with `readMaps`.
pub fn LinuxProcessTable_calcLibSize_helper() {
    todo!("port of LinuxProcessTable.c:727 — foreach-closure model; LibraryData not an Object")
}

/// TODO: port of `static void LinuxProcessTable_readMaps(LinuxProcess*
/// process, openat_arg_t procFd, const LinuxMachine* host, bool calcSize,
/// bool checkDeletedLib)` from `LinuxProcessTable.c:745`. `Hashtable` *is*
/// ported now, but the `calcSize` path still cannot be expressed faithfully:
/// the C does `LibraryData* libdata = Hashtable_get(ht, inode); ...
/// libdata->size += map_end - map_start;` — an in-place mutation through the
/// pointer returned by `Hashtable_get`. The ported
/// [`Hashtable_get`](crate::ported::hashtable::Hashtable_get) returns an
/// *immutable* `&dyn Object` and there is no htop `Hashtable_getMut` to port
/// (C mutates through the non-owning `void*` directly), so the aggregate
/// cannot be updated in place; additionally the file-local `LibraryData` type
/// is not modeled as an [`Object`](crate::ported::object::Object) (the value
/// the ported table stores). Stays stubbed until a mutable accessor + an
/// `Object`-modeled `LibraryData` exist.
pub fn LinuxProcessTable_readMaps() {
    todo!("port of LinuxProcessTable.c:745 — Hashtable_get is immutable; LibraryData not an Object")
}

/// Port of `LinuxProcessTable.c:840`. Reads `/proc/<pid>/statm`
/// (process-shared data): total program size and RSS (both scaled to KiB),
/// shared/text/data sizes, and derives private RSS. Thread tasks copy
/// `m_virt`/`m_resident` from the main task. The C `sscanf("%ld %ld ...")`
/// of the seven fields is modeled by whitespace-splitting and decimal
/// parsing, mirroring `sscanf`'s "stop at the first field that fails to
/// convert" semantics (and requiring all seven, `r == 7`, before scaling).
fn LinuxProcessTable_readStatmFile(
    process: &mut LinuxProcess,
    procFd: openat_arg_t,
    host: &LinuxMachine,
    mainTask: Option<&LinuxProcess>,
) -> bool {
    if let Some(mt) = mainTask {
        process.super_.m_virt = mt.super_.m_virt;
        process.super_.m_resident = mt.super_.m_resident;
        return true;
    }

    let mut statmdata = [0u8; 128];
    if Compat_readfileat(procFd, c"statm", &mut statmdata) < 1 {
        return false;
    }

    let nul = statmdata
        .iter()
        .position(|&b| b == 0)
        .unwrap_or(statmdata.len());
    let text = std::str::from_utf8(&statmdata[..nul]).unwrap_or("");

    // sscanf("%ld %ld %ld %ld %ld %ld %ld"): parse up to seven longs, stopping
    // at the first token that fails to convert (matching sscanf's return).
    let mut fields = [0i64; 7];
    let mut r = 0usize;
    for tok in text.split_ascii_whitespace() {
        if r >= 7 {
            break;
        }
        match tok.parse::<i64>() {
            Ok(v) => {
                fields[r] = v;
                r += 1;
            }
            Err(_) => break,
        }
    }

    // Assign the fields sscanf would have written (in order).
    if r >= 1 {
        process.super_.m_virt = fields[0];
    }
    if r >= 2 {
        process.super_.m_resident = fields[1];
    }
    if r >= 3 {
        process.m_share = fields[2];
    }
    if r >= 4 {
        process.m_trs = fields[3];
    }
    // fields[4] is unused since Linux 2.6 (always 0)
    if r >= 6 {
        process.m_drs = fields[5];
    }
    // fields[6] is unused since Linux 2.6 (always 0)

    if r == 7 {
        process.super_.m_virt *= host.pageSizeKB as i64;
        process.super_.m_resident *= host.pageSizeKB as i64;

        process.m_priv = process.super_.m_resident - (process.m_share * host.pageSizeKB as i64);
    }

    r == 7
}

/// TODO: port of `static bool LinuxProcessTable_readSmapsFile(LinuxProcess*
/// process, openat_arg_t procFd, bool haveSmapsRollup)` from
/// `LinuxProcessTable.c:897`. Blocked: the partial-line handling calls
/// `skipEndOfLine(FILE*)` (`generic`/`FileUtils`), which is not ported in the
/// tree, so the `fgets` chunk loop cannot be faithfully reproduced. Stays
/// stubbed until `skipEndOfLine` lands.
pub fn LinuxProcessTable_readSmapsFile() {
    todo!("port of LinuxProcessTable.c:897 — needs skipEndOfLine ported")
}

/// TODO: port of `static void LinuxProcessTable_readOpenVZData(LinuxProcess*
/// process, openat_arg_t procFd)` from `LinuxProcessTable.c:934` (guarded by
/// `#ifdef HAVE_OPENVZ`; only reached from the equally-guarded call site in
/// `recurseProcTree`). Blocked on three counts: (1) the partial-line handling
/// calls `skipEndOfLine(FILE*)` (`generic`/`FileUtils`), which is not ported;
/// (2) it reads/writes `process->ctid` (a `char*`) and `process->vpid`, but
/// neither field is modeled on [`LinuxProcess`] (only `m_lrs` et al. exist);
/// and (3) this build has not committed to the `HAVE_OPENVZ` variant. Stays
/// stubbed until those land.
pub fn LinuxProcessTable_readOpenVZData() {
    todo!("port of LinuxProcessTable.c:934 — needs skipEndOfLine + ctid/vpid fields + HAVE_OPENVZ")
}

/// Port of `static void LinuxProcessTable_readCGroupFile(LinuxProcess*
/// process, openat_arg_t procFd)` from `LinuxProcessTable.c:1024`. Reads
/// `/proc/<pid>/cgroup`, keeping the third `:`-delimited field of each line
/// (the cgroup path), joining them with `;` into a `PROC_LINE_LENGTH`-capped
/// `output` string, then updates the raw [`ProcessField::CGROUP`] width and
/// stores it. When the path changed it recomputes the shortened
/// [`CGroup_filterName`] ("CCGROUP") and [`CGroup_filterContainer`]
/// ("CONTAINER") forms (falling back to the raw cgroup / `"N/A"` widths); an
/// unchanged path only refreshes the widths from the cached short forms. A
/// missing file clears all three cached strings.
///
/// The C `output[PROC_LINE_LENGTH + 1]` buffer with the `at`/`left` cursor and
/// `snprintf` truncation is reproduced on a byte `Vec` with a `left` budget:
/// each group segment is truncated at `\n` (the C `*eol_w = '\0'`), a `;`
/// separator is charged one byte, and a segment that would overflow `left`
/// copies `left - 1` bytes and stops (the C truncation `break`). `fopenat` +
/// `fgets` become the ported [`fopenat`] + a [`BufRead::read_line`] loop.
/// `String_strchrnul`/`String_eq`/`free_and_xStrdup` map to the ported
/// helpers / `Option<String>` assignment.
fn LinuxProcessTable_readCGroupFile(process: &mut LinuxProcess, procFd: openat_arg_t) {
    use std::io::BufRead;

    let file = match fopenat(procFd, c"cgroup", "r") {
        Some(f) => f,
        None => {
            // free() + NULL all three cached strings.
            process.cgroup = None;
            process.cgroup_short = None;
            process.container_short = None;
            return;
        }
    };

    let mut output: Vec<u8> = Vec::new();
    let mut left = PROC_LINE_LENGTH;
    let mut reader = std::io::BufReader::new(file);
    let mut line = String::new();
    // while (!feof(file) && left > 0)
    while left > 0 {
        line.clear();
        // const char* ok = fgets(...); if (!ok) break;
        match reader.read_line(&mut line) {
            Ok(0) | Err(_) => break,
            Ok(_) => {}
        }

        let bytes = line.as_bytes();
        // Skip the first two ':'-delimited fields.
        let mut group = 0usize;
        for _ in 0..2 {
            group += String_strchrnul(&line[group..], b':');
            if group >= bytes.len() {
                // !*group — no further ':'
                break;
            }
            group += 1; // group++ past the ':'
        }

        // eol = strchrnul(group, '\n'); *eol_w = '\0';
        let group_end = group + String_strchrnul(&line[group..], b'\n');
        let group_bytes = &bytes[group..group_end];

        // if (at != output) { *at = ';'; at++; left--; }
        if !output.is_empty() {
            if left == 0 {
                break;
            }
            output.push(b';');
            left -= 1;
        }

        // int wrote = snprintf(at, left, "%s", group);
        let wrote = group_bytes.len();
        if wrote >= left {
            // Truncated: snprintf copies left - 1 bytes then we are done.
            let n = left.saturating_sub(1);
            output.extend_from_slice(&group_bytes[..n]);
            break;
        }
        output.extend_from_slice(group_bytes);
        left -= wrote;
    }
    // fclose(file) — reader dropped here.
    drop(reader);

    let output = String::from_utf8_lossy(&output).into_owned();

    // bool changed = !process->cgroup || !String_eq(process->cgroup, output);
    let changed = match &process.cgroup {
        Some(c) => !String_eq(c, &output),
        None => true,
    };

    Row_updateFieldWidth(ProcessField::CGROUP as RowField, output.len());
    // free_and_xStrdup(&process->cgroup, output);
    process.cgroup = Some(output);

    if !changed {
        // CCGROUP: from cached short form, else the raw cgroup width.
        match &process.cgroup_short {
            Some(cs) => Row_updateFieldWidth(ProcessField::CCGROUP as RowField, cs.len()),
            None => Row_updateFieldWidth(
                ProcessField::CCGROUP as RowField,
                process.cgroup.as_deref().unwrap().len(),
            ),
        }
        match &process.container_short {
            Some(cs) => Row_updateFieldWidth(ProcessField::CONTAINER as RowField, cs.len()),
            None => Row_updateFieldWidth(ProcessField::CONTAINER as RowField, "N/A".len()),
        }
        return;
    }

    // char* cgroup_short = CGroup_filterName(process->cgroup);
    let cgroup_short = CGroup_filterName(process.cgroup.as_deref().unwrap());
    match cgroup_short {
        Some(cs) => {
            Row_updateFieldWidth(ProcessField::CCGROUP as RowField, cs.len());
            process.cgroup_short = Some(cs);
        }
        None => {
            // CCGROUP aliases the normal CGROUP if shortening fails.
            Row_updateFieldWidth(
                ProcessField::CCGROUP as RowField,
                process.cgroup.as_deref().unwrap().len(),
            );
            process.cgroup_short = None;
        }
    }

    // char* container_short = CGroup_filterContainer(process->cgroup);
    let container_short = CGroup_filterContainer(process.cgroup.as_deref().unwrap());
    match container_short {
        Some(cs) => {
            Row_updateFieldWidth(ProcessField::CONTAINER as RowField, cs.len());
            process.container_short = Some(cs);
        }
        None => {
            // CONTAINER is just "N/A" if shortening fails.
            Row_updateFieldWidth(ProcessField::CONTAINER as RowField, "N/A".len());
            process.container_short = None;
        }
    }
}

/// Port of `LinuxProcessTable.c:1022`. Reads `/proc/<pid>/oom_score` into the
/// [`LinuxProcess`] `oom` field (thread tasks copy from the main task).
/// Defaults to `UINT_MAX` and only accepts a value terminated by NUL, `\n`,
/// or space, exactly as the C guards. `fast_strtoull_dec` is capped at the
/// number of bytes read.
fn LinuxProcessTable_readOomData(
    process: &mut LinuxProcess,
    procFd: openat_arg_t,
    mainTask: Option<&LinuxProcess>,
) {
    if let Some(mt) = mainTask {
        process.oom = mt.oom;
        return;
    }

    let mut buffer = [0u8; PROC_LINE_LENGTH + 1];

    process.oom = u32::MAX; // UINT_MAX
    let oomRead = Compat_readfileat(procFd, c"oom_score", &mut buffer);
    if oomRead < 1 {
        return;
    }

    let mut cur: &[u8] = &buffer[..];
    let oom = fast_strtoull_dec(&mut cur, oomRead as usize);
    let next = buffer.len() - cur.len();
    let c = buffer.get(next).copied().unwrap_or(0);
    if c != 0 && c != b'\n' && c != b' ' {
        return;
    }

    if oom > u32::MAX as u64 {
        return;
    }

    process.oom = oom as u32;
}

/// Port of `LinuxProcessTable.c:1052`. Reads `/proc/<pid>/autogroup` (CFS
/// autogroup id + nice), copying from the main task for threads. The C
/// `sscanf("/autogroup-%ld nice %d", ...)` (requiring both fields, `ok == 2`)
/// is modeled by a prefix strip + whitespace split. `autogroup_id` stays `-1`
/// on any parse failure.
fn LinuxProcessTable_readAutogroup(
    process: &mut LinuxProcess,
    procFd: openat_arg_t,
    mainTask: Option<&LinuxProcess>,
) {
    if let Some(mt) = mainTask {
        process.autogroup_id = mt.autogroup_id;
        return;
    }

    process.autogroup_id = -1;

    let mut autogroup = [0u8; 64];
    let amtRead = Compat_readfileat(procFd, c"autogroup", &mut autogroup);
    if amtRead < 0 {
        return;
    }

    let nul = autogroup
        .iter()
        .position(|&b| b == 0)
        .unwrap_or(autogroup.len());
    let content = std::str::from_utf8(&autogroup[..nul]).unwrap_or("");

    // "/autogroup-%ld nice %d"
    let parsed = (|| -> Option<(i64, i32)> {
        let rest = content.strip_prefix("/autogroup-")?;
        let mut it = rest.split_whitespace();
        let identity: i64 = it.next()?.parse().ok()?;
        if it.next()? != "nice" {
            return None;
        }
        let nice: i32 = it.next()?.parse().ok()?;
        Some((identity, nice))
    })();

    if let Some((identity, nice)) = parsed {
        process.autogroup_id = identity;
        process.autogroup_nice = nice;
    }
}

/// Port of `static void LinuxProcessTable_readSecattrData(LinuxProcess*
/// process, openat_arg_t procFd, const LinuxProcess* mainTask)` from
/// `LinuxProcessTable.c:1182`. Thread tasks copy the main task's `secattr`
/// (or clear it when absent). For a main task it reads `/proc/<pid>/attr/current`
/// (the SELinux/AppArmor security context), clears `secattr` on a short read
/// (`< 1`), otherwise trims at the first `\n`, updates the
/// [`ProcessField::SECATTR`] column width, and stores the value.
fn LinuxProcessTable_readSecattrData(
    process: &mut LinuxProcess,
    procFd: openat_arg_t,
    mainTask: Option<&LinuxProcess>,
) {
    if let Some(mt) = mainTask {
        // free_and_xStrdup(&process->secattr, mainSecAttr) or free + NULL.
        process.secattr = mt.secattr.clone();
        return;
    }

    let mut buffer = [0u8; PROC_LINE_LENGTH + 1];
    let attrdata = Compat_readfileat(procFd, c"attr/current", &mut buffer);
    if attrdata < 1 {
        process.secattr = None;
        return;
    }

    // char* newline = strchr(buffer, '\n'); if (newline) *newline = '\0';
    // strlen stops at the newline (or the NUL terminator otherwise).
    let end = buffer
        .iter()
        .position(|&b| b == b'\n' || b == 0)
        .unwrap_or(buffer.len());
    let text = String::from_utf8_lossy(&buffer[..end]).into_owned();

    Row_updateFieldWidth(ProcessField::SECATTR as RowField, text.len());
    process.secattr = Some(text);
}

/// Port of `LinuxProcessTable.c:1111`. Resolves `/proc/<pid>/cwd` (the
/// process working directory) via `readlinkat`, storing it in
/// [`Process::procCwd`]; threads copy from the main task. The C
/// `#if HAVE_READLINKAT && HAVE_OPENAT` branch (the one this build commits
/// to) is ported; the `Compat_readlink` fallback is the other build variant.
fn LinuxProcessTable_readCwd(
    process: &mut LinuxProcess,
    procFd: openat_arg_t,
    mainTask: Option<&LinuxProcess>,
) {
    if let Some(mt) = mainTask {
        // free_and_xStrdup(mainCwd) when set, else free + NULL.
        process.super_.procCwd = mt.super_.procCwd.clone();
        return;
    }

    let mut pathBuffer = [0u8; PATH_MAX + 1];
    let r = unsafe {
        libc::readlinkat(
            procFd,
            c"cwd".as_ptr(),
            pathBuffer.as_mut_ptr() as *mut libc::c_char,
            pathBuffer.len() - 1,
        )
    };

    if r < 0 {
        process.super_.procCwd = None;
        return;
    }

    process.super_.procCwd = Some(String::from_utf8_lossy(&pathBuffer[..r as usize]).into_owned());
}

/// Port of `LinuxProcessTable.c:1145`. Resolves `/proc/<pid>/exe` via
/// `readlinkat`, handling the kernel `" (deleted)"` suffix (stripping it and
/// flagging `procExeDeleted`), and updates the executable path through
/// [`Process_updateExe`]. Threads copy from the main task. The
/// suffix/comparison logic runs on raw bytes (paths may not be UTF-8);
/// the final value is handed to `Process_updateExe` as a (lossily-decoded)
/// string, matching the `Option<String> procExe` model. The
/// `HAVE_READLINKAT && HAVE_OPENAT` branch is ported (committed build
/// variant).
fn LinuxProcessList_readExe(
    process: &mut Process,
    procFd: openat_arg_t,
    mainTask: Option<&LinuxProcess>,
) {
    if let Some(mt) = mainTask {
        Process_updateExe(process, mt.super_.procExe.as_deref());
        process.procExeDeleted = mt.super_.procExeDeleted;
        return;
    }

    let mut filename = [0u8; PATH_MAX + 1];
    let amtRead = unsafe {
        libc::readlinkat(
            procFd,
            c"exe".as_ptr(),
            filename.as_mut_ptr() as *mut libc::c_char,
            filename.len() - 1,
        )
    };

    if amtRead > 0 {
        let mut fbytes = filename[..amtRead as usize].to_vec();

        // if (!procExe || (!procExeDeleted && !String_eq(filename, procExe)) || procExeDeleted)
        let differs = process
            .procExe
            .as_deref()
            .map(|e| e.as_bytes() != fbytes.as_slice())
            .unwrap_or(true);
        // Faithful mirror of the C boolean; kept verbatim to match the SPEC.
        #[allow(clippy::nonminimal_bool)]
        let cond = process.procExe.is_none()
            || (!process.procExeDeleted && differs)
            || process.procExeDeleted;

        if cond {
            const DELETED_MARKER: &[u8] = b" (deleted)";
            let markerLen = DELETED_MARKER.len();
            let filenameLen = fbytes.len();

            if filenameLen > markerLen {
                let oldExeDeleted = process.procExeDeleted;

                process.procExeDeleted = &fbytes[filenameLen - markerLen..] == DELETED_MARKER;

                if process.procExeDeleted {
                    fbytes.truncate(filenameLen - markerLen);
                }

                if oldExeDeleted != process.procExeDeleted {
                    process.mergedCommand.lastUpdate = 0;
                }
            }

            let s = String::from_utf8_lossy(&fbytes).into_owned();
            Process_updateExe(process, Some(&s));
        }
    } else if process.procExe.is_some() {
        Process_updateExe(process, None);
        process.procExeDeleted = false;
    }
}

/// Port of `LinuxProcessTable.c:1194`. Reads a whole `/proc` file whose size
/// is not known in advance, growing the buffer (starting at 512 bytes,
/// doubling) up to `MAX_CMDLINE_BUFFER_SIZE` while each read fills the buffer.
/// The C `char*` result + `ssize_t* amtRead` out-param become a returned
/// `Some((buffer, amtRead))`; `None` mirrors the C `NULL` (nothing read /
/// error). The buffer keeps its full allocated length (data is NUL-terminated
/// at `amtRead` by [`Compat_readfileat`]), matching the C caller expectations.
fn readFileDynamic(procFd: openat_arg_t, filename: &CStr) -> Option<(Vec<u8>, ssize_t)> {
    let mut bufferSize: usize = 512;
    let mut buffer = vec![0u8; bufferSize];

    let mut amtRead = Compat_readfileat(procFd, filename, &mut buffer);

    // If the buffer was full, the file might be larger; retry with more space.
    while amtRead > 0 && amtRead as usize == bufferSize - 1 && bufferSize < MAX_CMDLINE_BUFFER_SIZE
    {
        bufferSize *= 2;
        buffer.resize(bufferSize, 0);
        amtRead = Compat_readfileat(procFd, filename, &mut buffer);
    }

    if amtRead <= 0 {
        return None;
    }

    Some((buffer, amtRead))
}

/// Port of `LinuxProcessTable.c:1219`. Reads `/proc/<pid>/cmdline`, first
/// refreshing the exe link ([`LinuxProcessList_readExe`]), then splitting the
/// NUL-delimited argument vector and computing the basename token
/// `[tokenStart, tokenEnd)` for display. Ports the full argument-parsing
/// heuristic for processes that flatten their cmdline with spaces (e.g.
/// chrome), including the `faccessat` path-existence cross-validation. The C
/// `char*` cursor arithmetic on the mutable buffer is modeled with byte
/// indices into a `Vec<u8>`; `(size_t)-1` sentinels map to [`usize::MAX`]
/// (`NPOS`), whose unsigned comparisons match C `size_t` exactly.
///
/// Signature mapping: takes the concrete `&mut Process` (the C `Process*`);
/// `mainTask` is the [`Option`] of a borrowed [`LinuxProcess`].
fn LinuxProcessTable_readCmdlineFile(
    process: &mut Process,
    procFd: openat_arg_t,
    mainTask: Option<&LinuxProcess>,
) -> bool {
    LinuxProcessList_readExe(process, procFd, mainTask);

    let (mut command, amtRead) = match readFileDynamic(procFd, c"cmdline") {
        Some(v) => v,
        None => return false,
    };
    let amtRead = amtRead as usize;

    const NPOS: usize = usize::MAX; // (size_t)-1

    let mut tokenEnd = NPOS;
    let mut tokenStart = NPOS;
    let mut lastChar = 0usize;
    let mut argSepNUL = false;
    let mut argSepSpace = false;

    for i in 0..amtRead {
        let argChar = command[i];

        // newline used as delimiter -> non-printable placeholder
        if argChar == b'\n' {
            command[i] = b'\r';
            continue;
        }

        if argChar == b'\0' {
            command[i] = b'\n';

            if tokenEnd == NPOS {
                tokenEnd = i;
            }

            continue;
        }

        // NUL byte in the middle of command
        if tokenEnd != NPOS {
            argSepNUL = true;
        }

        if argChar <= b' ' {
            argSepSpace = true;
        }

        // last '/' before end of token = start of basename
        if argChar == b'/' && tokenEnd == NPOS {
            tokenStart = i + 1;
        }

        lastChar = i;
    }

    command[lastChar + 1] = b'\0';

    // faccessat(AT_FDCWD, bytes, F_OK, AT_SYMLINK_NOFOLLOW); interior NUL -> -1.
    let faccess = |bytes: &[u8]| -> i32 {
        match std::ffi::CString::new(bytes) {
            Ok(cs) => Compat_faccessat(libc::AT_FDCWD, &cs, libc::F_OK, libc::AT_SYMLINK_NOFOLLOW),
            Err(_) => -1,
        }
    };

    if !argSepNUL && argSepSpace {
        /* Argument parsing heuristic for processes that flatten their
         * command line with spaces instead of NUL bytes. */
        tokenStart = NPOS;
        tokenEnd = NPOS;

        let exeLen = process.procExe.as_ref().map(|s| s.len()).unwrap_or(0);

        let starts_with_exe = process
            .procExe
            .as_deref()
            .map(|e| command[..=lastChar].starts_with(e.as_bytes()))
            .unwrap_or(false);

        if process.procExe.is_some()
            && starts_with_exe
            && exeLen < lastChar
            && command[exeLen] <= b' '
        {
            tokenStart = process.procExeBasenameOffset;
            tokenEnd = exeLen;
        }
        // Check if the space is part of a filename for an existing file.
        else if faccess(&command[..=lastChar]) != 0 {
            // Path does not exist; search for the part that does.
            let mut tokenArg0Start = NPOS;

            for i in 0..=lastChar {
                let cmdChar = command[i];

                if cmdChar <= b' ' {
                    if tokenEnd != NPOS {
                        // Split on every further separator
                        command[i] = b'\n';
                        continue;
                    }

                    // Found our first argument
                    command[i] = b'\0';

                    let found = faccess(&command[..i]) == 0;

                    // Restore if this wasn't it
                    command[i] = if found { b'\n' } else { cmdChar };

                    if found {
                        tokenEnd = i;
                    }
                    if tokenArg0Start == NPOS {
                        tokenArg0Start = if tokenStart == NPOS { 0 } else { tokenStart };
                    }

                    continue;
                }

                if tokenEnd != NPOS {
                    continue;
                }

                if cmdChar == b'/' {
                    // Normal path separator
                    tokenStart = i + 1;
                } else if cmdChar == b'\\'
                    && (tokenStart == NPOS || tokenStart == 0 || command[tokenStart - 1] == b'\\')
                {
                    // Windows Path separator (WINE)
                    tokenStart = i + 1;
                } else if cmdChar == b':' && (command[i + 1] != b'/' && command[i + 1] != b'\\') {
                    // Colon not part of a Windows Path
                    tokenEnd = i;
                } else if tokenStart == NPOS {
                    // Relative path
                    tokenStart = i;
                }
            }

            if tokenEnd == NPOS {
                tokenStart = tokenArg0Start;

                // No token delimiter found, forcibly split
                for i in 0..=lastChar {
                    if command[i] <= b' ' {
                        command[i] = b'\n';
                        if tokenEnd == NPOS {
                            tokenEnd = i;
                        }
                    }
                }
            }
        }

        // Reset if start is behind end.
        if tokenStart >= tokenEnd {
            tokenStart = NPOS;
            tokenEnd = NPOS;
        }
    }

    if tokenStart == NPOS {
        tokenStart = 0;
    }

    if tokenEnd == NPOS {
        tokenEnd = lastChar + 1;
    }

    let s = String::from_utf8_lossy(&command[..=lastChar]).into_owned();
    Process_updateCmdline(process, Some(&s), tokenStart, tokenEnd);

    true
}

/// Port of `LinuxProcessTable.c:1396`. Reads `/proc/<pid>/comm` (the process
/// "command" name) and updates it via [`Process_updateComm`]; a failed read
/// clears it (`None`). The C `command[amtRead - 1] = '\0'` drops the trailing
/// newline, modeled by slicing off the last byte.
fn LinuxProcessList_readComm(process: &mut Process, procFd: openat_arg_t) {
    match readFileDynamic(procFd, c"comm") {
        Some((command, amtRead)) => {
            let end = (amtRead as usize).saturating_sub(1);
            let s = String::from_utf8_lossy(&command[..end]).into_owned();
            Process_updateComm(process, Some(&s));
        }
        None => Process_updateComm(process, None),
    }
}

/// TODO: port of `static char* LinuxProcessTable_updateTtyDevice(TtyDriver*
/// ttyDrivers, unsigned long int tty_nr)` from `LinuxProcessTable.c:1514`.
/// Blocked: the body decomposes `tty_nr` and each candidate `st_rdev` with
/// the `major()`/`minor()` device-number macros (from `sys/sysmacros.h` /
/// `sys/mkdev.h`), which are not ported anywhere in the tree — and their
/// glibc bit-layout must match how the kernel encodes `tty_nr` for the
/// comparisons to be correct. Porting a subtly-wrong `major`/`minor` here
/// would corrupt every tty-name lookup, so this stays stubbed until those
/// macros are modeled. (Only consumer is the stubbed `recurseProcTree`.)
pub fn LinuxProcessTable_updateTtyDevice() {
    todo!("port of LinuxProcessTable.c:1514 — needs major()/minor() device-number macros")
}

/// Port of `LinuxProcessTable.c:1466`. True iff `proc` has been alive for
/// more than `seconds`, using the host's current realtime clock and the
/// process's parsed start time. Reads `proc->super.host->realtimeMs` through
/// the opaque `*const Machine` handle (the `GPU_readProcessData` idiom).
/// Returns `false` while the start time is not yet parsed.
fn isOlderThan(proc: &Process, seconds: u32) -> bool {
    let host = proc.super_.host as *const Machine;
    let realtimeMs = unsafe { (*host).realtimeMs };

    debug_assert!(realtimeMs > 0);

    /* Starttime might not yet be parsed */
    if proc.starttime_ctime <= 0 {
        return false;
    }

    let realtime = realtimeMs / 1000;

    if realtime < proc.starttime_ctime as u64 {
        return false;
    }

    realtime - proc.starttime_ctime as u64 > seconds as u64
}

/// TODO: port of `static bool LinuxProcessTable_recurseProcTree(
/// LinuxProcessTable* this, openat_arg_t parentFd, const LinuxMachine* lhost,
/// const char* dirname, const LinuxProcess* mainTask)` from
/// `LinuxProcessTable.c:1588`. Blocked at its core: it obtains each process
/// via `ProcessTable_getProcess(pt, pid, &preExisting, LinuxProcess_new)` and
/// registers it with `ProcessTable_add(pt, proc)` / `ProcessTable_findProcess`,
/// but the ported [`ProcessTable`]/`Table` store rows as `Row` values (not the
/// polymorphic `Process*` htop holds), so `ProcessTable_getProcess`/`_add` are
/// themselves stubbed (see `processtable.rs`) — there is no `Process` to fetch,
/// mutate, or add. It also depends on several still-stubbed leaves
/// (`updateUser`, `readIoFile`, `readMaps`, `readSmapsFile`, `readCGroupFile`,
/// `readSecattrData`, `updateTtyDevice`) and on `GPU_readProcessData` /
/// `Process_fillStarttimeBuffer`. Stays stubbed until the process-typed table
/// lands.
pub fn LinuxProcessTable_recurseProcTree() {
    todo!("port of LinuxProcessTable.c:1588 — needs ProcessTable_getProcess/_add (process-typed table)")
}

/// TODO: port of `void ProcessTable_goThroughEntries(ProcessTable* super)`
/// from `LinuxProcessTable.c:1951`. Blocked: its whole job is to kick off the
/// `/proc` walk via [`LinuxProcessTable_recurseProcTree`] (stubbed above), and
/// it also queries `LinuxProcess_isAutogroupEnabled()` (a stub in
/// `linuxprocess.rs`) and shifts the `LinuxMachine` GPU-engine linked list.
/// Cannot be ported faithfully until `recurseProcTree` is unblocked.
pub fn ProcessTable_goThroughEntries() {
    todo!("port of LinuxProcessTable.c:1951 — delegates to the stubbed recurseProcTree")
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn fast_strtoull_dec_parses_and_advances() {
        let s = b"12345rest";
        let mut cur: &[u8] = s;
        assert_eq!(fast_strtoull_dec(&mut cur, 0), 12345);
        assert_eq!(cur, b"rest");

        // maxlen caps the number of digits consumed.
        let mut cur2: &[u8] = b"12345";
        assert_eq!(fast_strtoull_dec(&mut cur2, 3), 123);
        assert_eq!(cur2, b"45");

        // Empty / non-digit input yields 0 and does not advance.
        let mut cur3: &[u8] = b"abc";
        assert_eq!(fast_strtoull_dec(&mut cur3, 0), 0);
        assert_eq!(cur3, b"abc");
    }

    #[test]
    fn fast_strtoll_dec_handles_sign() {
        let mut cur: &[u8] = b"-42 ";
        assert_eq!(fast_strtoll_dec(&mut cur, 0), -42);
        assert_eq!(cur, b" ");

        let mut cur2: &[u8] = b"7";
        assert_eq!(fast_strtoll_dec(&mut cur2, 0), 7);
    }

    #[test]
    fn fast_strtoi_and_strtol_and_strtoul() {
        let mut cur: &[u8] = b"-2147483648";
        assert_eq!(fast_strtoi_dec(&mut cur, 0), i32::MIN);

        let mut cur2: &[u8] = b"-5";
        assert_eq!(fast_strtol_dec(&mut cur2, 0), -5);

        let mut cur3: &[u8] = b"100";
        assert_eq!(fast_strtoul_dec(&mut cur3, 0), 100);
    }

    #[test]
    fn fast_strtoull_hex_parses_mixed_case() {
        let mut cur: &[u8] = b"deadBEEF!";
        assert_eq!(fast_strtoull_hex(&mut cur, 0), 0xdeadbeef);
        assert_eq!(cur, b"!");

        let mut cur2: &[u8] = b"ff";
        assert_eq!(fast_strtoull_hex(&mut cur2, 0), 0xff);

        // Non-hex input stops immediately at 0.
        let mut cur3: &[u8] = b"zzz";
        assert_eq!(fast_strtoull_hex(&mut cur3, 0), 0);
        assert_eq!(cur3, b"zzz");
    }

    #[test]
    fn strtopid_accepts_valid_and_rejects_junk() {
        assert_eq!(strtopid("1234"), 1234);
        assert_eq!(strtopid("0"), 0); // zero is not a valid pid
        assert_eq!(strtopid("12a"), 0); // trailing garbage
        assert_eq!(strtopid(""), 0);
        assert_eq!(strtopid("-5"), 0); // negative wraps huge -> rejected
    }

    #[test]
    fn sortTtyDrivers_orders_by_major_then_minor() {
        let a = TtyDriver {
            path: None,
            major: 4,
            minorFrom: 64,
            minorTo: 95,
        };
        let b = TtyDriver {
            path: None,
            major: 4,
            minorFrom: 0,
            minorTo: 63,
        };
        let c = TtyDriver {
            path: None,
            major: 5,
            minorFrom: 0,
            minorTo: 1,
        };

        assert_eq!(sortTtyDrivers(&a, &b), 1);
        assert_eq!(sortTtyDrivers(&b, &a), -1);
        assert_eq!(sortTtyDrivers(&a, &c), -1);
        assert_eq!(sortTtyDrivers(&a, &a), 0);
    }

    #[test]
    fn isOlderThan_compares_against_host_realtime() {
        use crate::ported::machine::Machine;
        use crate::ported::process::Process;
        use core::ffi::c_void;

        let mut host = Machine::default();
        host.realtimeMs = 100_000; // 100 s of realtime

        let mut proc = Process::default();
        proc.super_.host = &host as *const Machine as *const c_void;

        // Alive since t=50s -> 50s old: older than 10s, not older than 60s.
        proc.starttime_ctime = 50;
        assert!(isOlderThan(&proc, 10));
        assert!(!isOlderThan(&proc, 60));

        // Unparsed start time (<= 0) is never "older than".
        proc.starttime_ctime = 0;
        assert!(!isOlderThan(&proc, 0));
    }

    #[test]
    fn getProcessState_maps_known_and_unknown() {
        assert_eq!(
            LinuxProcessTable_getProcessState(b'R'),
            ProcessState::RUNNING
        );
        assert_eq!(
            LinuxProcessTable_getProcessState(b'S'),
            ProcessState::SLEEPING
        );
        assert_eq!(
            LinuxProcessTable_getProcessState(b'Z'),
            ProcessState::ZOMBIE
        );
        assert_eq!(
            LinuxProcessTable_getProcessState(b'D'),
            ProcessState::UNINTERRUPTIBLE_WAIT
        );
        assert_eq!(
            LinuxProcessTable_getProcessState(b'?'),
            ProcessState::UNKNOWN
        );
    }
}