libxml-rs 0.1.0-alpha.21

//! XSLT document() function support (§33, §85 Phase 8).
//!
//! The `document()` function loads external XML documents during a
//! transformation. Documents are cached per transform context so repeated
//! loads of the same URI reuse the same document.
//!
//! # UPSTREAM-PARITY
//!
//! Upstream libxslt (documents.c) maintains a document cache on the
//! transform context (`docCache` hash). `xsltLoadDocument` resolves the
//! URI relative to the source document's base, loads it through the
//! configured loader (default: file/network), and caches the result.
//!
//! The loader function can be overridden with `xsltSetLoaderFunc`.

use crate::abi::structs::*;
use crate::abi::types::*;
use std::os::raw::c_int;
use std::ptr;

/// The XSLT document cache entry.
#[repr(C)]
pub struct _xsltDocCacheEntry {
    pub next: *mut _xsltDocCacheEntry,
    pub uri: *mut xmlChar,
    pub doc: *mut _xmlDoc,
}

/// Register a result-tree-fragment (RVT) document in the context's document
/// cache so it is freed exactly once at transform-context teardown
/// (`xsltFreeDocCache` releases every cached doc).
///
/// The entry carries a NULL URI, so `cache_lookup` (which requires a
/// non-NULL, matching URI) never matches it.
///
/// # UPSTREAM-PARITY
///
/// Upstream libxslt tracks RVT documents on the context (variables.c
/// `xsltCreateRVT`) and frees them with the context; we reuse the docCache
/// list for the same lifecycle.
///
/// # SAFETY
///
/// - `ctxt` must be a valid `_xsltTransformContext`.
/// - Ownership of `doc` transfers to the cache (freed at teardown).
pub(crate) unsafe fn xsltRegisterRVT(ctxt: *mut _xsltTransformContext, doc: *mut _xmlDoc) {
    if ctxt.is_null() || doc.is_null() {
        return;
    }
    let entry =
        libc::calloc(1, core::mem::size_of::<_xsltDocCacheEntry>()) as *mut _xsltDocCacheEntry;
    if entry.is_null() {
        return;
    }
    (*entry).uri = ptr::null_mut();
    (*entry).doc = doc;
    // UPSTREAM-PARITY: the candidate's RVT/cached-doc list head lives in the
    // `cache` slot (xsltTransformCachePtr upstream; unused by the candidate
    // for that purpose — documented divergence).
    (*entry).next = (*ctxt).cache as *mut _xsltDocCacheEntry;
    (*ctxt).cache = entry as *mut c_void;
}

/// Default XSLT loader function (file loading).
///
/// # SAFETY
///
/// - `ctxt` may be NULL.
/// - `URI` must be a valid NUL-terminated string.
pub unsafe extern "C" fn xsltDefaultLoader(
    _ctxt: *mut c_void,
    _style: *const c_char,
    URI: *const c_char,
    _ns: *const c_char,
    _secondary: c_int,
) -> *mut _xmlParserInput {
    if URI.is_null() {
        return ptr::null_mut();
    }
    // Phase 8: load the URI via the XML parser I/O layer.
    ptr::null_mut()
}

/// Global loader function (set via xsltSetLoaderFunc).
static mut XSLT_LOADER: Option<
    unsafe extern "C" fn(
        *mut c_void,
        *const c_char,
        *const c_char,
        *const c_char,
        c_int,
    ) -> *mut _xmlParserInput,
> = None;

/// Set the global XSLT loader function.
///
/// # SAFETY
///
/// - `loader` must be a valid function pointer or NULL.
#[no_mangle]
pub unsafe extern "C" fn xsltSetLoaderFunc(
    loader: Option<
        unsafe extern "C" fn(
            *mut c_void,
            *const c_char,
            *const c_char,
            *const c_char,
            c_int,
        ) -> *mut _xmlParserInput,
    >,
) {
    XSLT_LOADER = loader;
}

/// Get the current global loader function.
pub fn xsltGetLoaderFunc() -> Option<
    unsafe extern "C" fn(
        *mut c_void,
        *const c_char,
        *const c_char,
        *const c_char,
        c_int,
    ) -> *mut _xmlParserInput,
> {
    // SAFETY: only mutated by xsltSetLoaderFunc; safe to read here.
    unsafe { XSLT_LOADER }
}

/// Load a document by URI, using the cache.
///
/// Returns the loaded document (owned by the cache) or NULL on error.
///
/// # SAFETY
///
/// - `ctxt` must be a valid `_xsltTransformContext`.
/// - `URI` must be a valid NUL-terminated string.
pub unsafe fn xsltLoadDocument(
    ctxt: *mut _xsltTransformContext,
    URI: *const xmlChar,
) -> *mut _xmlDoc {
    if ctxt.is_null() || URI.is_null() {
        return ptr::null_mut();
    }
    // Check the cache first.
    if let Some(cached) = cache_lookup(ctxt, URI) {
        return cached;
    }
    // Resolve the URI against the source document's base.
    let base = if !(*ctxt).document.is_null()
        && !(*(*ctxt).document).doc.is_null()
        && !(*(*(*ctxt).document).doc).URL.is_null()
    {
        let len = libc::strlen((*(*(*ctxt).document).doc).URL as *const libc::c_char) as usize;
        Some(core::slice::from_raw_parts(
            (*(*(*ctxt).document).doc).URL,
            len,
        ))
    } else {
        None
    };
    let uri_bytes =
        core::slice::from_raw_parts(URI, libc::strlen(URI as *const libc::c_char) as usize);
    let resolved: Option<Vec<u8>> = match base {
        Some(b) => crate::xml::uri::resolve_uri(b, uri_bytes),
        None => Some(uri_bytes.to_vec()),
    };
    let resolved = match resolved {
        Some(r) if !r.is_empty() => r,
        _ => return ptr::null_mut(),
    };
    // Load via the configured loader or the default file loader.
    let mut cstr = resolved.clone();
    cstr.push(0);
    let doc = load_via_loader(ctxt, cstr.as_ptr() as *mut xmlChar);
    if !doc.is_null() {
        cache_store(ctxt, URI, doc);
    }
    doc
}

/// Load a document via the configured loader.
///
/// Uses the global loader function if set; otherwise parses the URI as a
/// local file. Returns a parsed document or NULL on failure.
///
/// # SAFETY
///
/// - All pointers must be valid.
unsafe fn load_via_loader(ctxt: *mut _xsltTransformContext, uri: *mut xmlChar) -> *mut _xmlDoc {
    // If a custom loader is configured, invoke it.
    let loader = xsltGetLoaderFunc();
    if let Some(loader_fn) = loader {
        let input = loader_fn(
            ctxt as *mut c_void,
            ptr::null(), // style
            uri as *const c_char,
            ptr::null(), // ns
            0,           // secondary
        );
        if !input.is_null() {
            // The loader returned a parser input; we currently cannot feed
            // it into a document without a parser context, so free it.
            crate::xml::parser::helpers::free_parser_input(input);
        }
    }
    // Default: parse the URI as a file path.
    crate::abi::exports_xml2::xmlReadFile(uri as *const c_char, ptr::null(), 0)
}

/// Look up a document in the context's cache.
///
/// # SAFETY
///
/// - All pointers must be valid.
unsafe fn cache_lookup(
    ctxt: *mut _xsltTransformContext,
    uri: *const xmlChar,
) -> Option<*mut _xmlDoc> {
    let mut cur = (*ctxt).cache as *mut _xsltDocCacheEntry;
    while !cur.is_null() {
        if !(*cur).uri.is_null()
            && libc::strcmp(
                (*cur).uri as *const libc::c_char,
                uri as *const libc::c_char,
            ) == 0
        {
            return Some((*cur).doc);
        }
        cur = (*cur).next;
    }
    None
}

/// Store a document in the context's cache.
///
/// # SAFETY
///
/// - All pointers must be valid.
unsafe fn cache_store(ctxt: *mut _xsltTransformContext, uri: *const xmlChar, doc: *mut _xmlDoc) {
    let entry =
        libc::calloc(1, core::mem::size_of::<_xsltDocCacheEntry>()) as *mut _xsltDocCacheEntry;
    if entry.is_null() {
        return;
    }
    let len = libc::strlen(uri as *const libc::c_char);
    let copy = libc::malloc(len + 1) as *mut xmlChar;
    if copy.is_null() {
        libc::free(entry as *mut libc::c_void);
        return;
    }
    libc::memcpy(copy as *mut libc::c_void, uri as *const libc::c_void, len);
    *copy.add(len) = 0;
    (*entry).uri = copy;
    (*entry).doc = doc;
    (*entry).next = (*ctxt).cache as *mut _xsltDocCacheEntry;
    (*ctxt).cache = entry as *mut c_void;
}

/// Free the document cache of a transform context.
///
/// # SAFETY
///
/// - `ctxt` must be a valid `_xsltTransformContext`.
pub unsafe fn xsltFreeDocCache(ctxt: *mut _xsltTransformContext) {
    if ctxt.is_null() {
        return;
    }
    let mut cur = (*ctxt).cache as *mut _xsltDocCacheEntry;
    (*ctxt).cache = ptr::null_mut();
    while !cur.is_null() {
        let next = (*cur).next;
        if !(*cur).uri.is_null() {
            libc::free((*cur).uri as *mut libc::c_void);
        }
        if !(*cur).doc.is_null() {
            crate::xml::tree::free_doc((*cur).doc);
        }
        libc::free(cur as *mut libc::c_void);
        cur = next;
    }
}

use std::ffi::c_void;
use std::os::raw::c_char;

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

    #[test]
    fn test_null_args() {
        unsafe {
            assert!(xsltLoadDocument(ptr::null_mut(), ptr::null()).is_null());
            xsltFreeDocCache(ptr::null_mut());
        }
    }
}