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/*******************************************************************************
*
* Copyright (c) 2026 Haixing Hu.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0.
*
******************************************************************************/
use std::io::{
Read,
Result,
};
use crate::util::read_utf8_payload as read_utf8_payload_impl;
use crate::{
BinaryReadExt,
ByteOrder,
Leb128ReadExt,
};
/// Extension methods for reading length-prefixed UTF-8 strings.
pub trait StringReadExt: Read {
/// Reads a UTF-8 payload with an already decoded byte length.
///
/// # Parameters
/// - `len`: UTF-8 payload length in bytes.
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for payload reads, [`std::io::ErrorKind::InvalidData`] when
/// `len` exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`] when the payload
/// is not valid UTF-8.
fn read_utf8_payload(&mut self, len: usize, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with an unsigned LEB128 byte-length prefix.
///
/// The length prefix is decoded as `usize`, so this format is target-width
/// dependent. Prefer `u16` or `u32` length-prefix methods for persistent
/// files and cross-platform protocols.
///
/// # Parameters
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_uleb(&mut self, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a canonical unsigned LEB128 byte-length prefix.
///
/// The length prefix is decoded as `usize`, so this format is target-width
/// dependent. Prefer `u16` or `u32` length-prefix methods for persistent
/// files and cross-platform protocols.
///
/// # Parameters
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the length prefix is malformed or non-canonical, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_uleb_strict(&mut self, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a runtime-order `u16` byte-length prefix.
///
/// # Parameters
/// - `byte_order`: Byte order used by the length prefix.
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_u16(&mut self, byte_order: ByteOrder, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a big-endian `u16` byte-length prefix.
///
/// # Parameters
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_u16_be(&mut self, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a little-endian `u16` byte-length prefix.
///
/// # Parameters
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_u16_le(&mut self, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a runtime-order `u32` byte-length prefix.
///
/// # Parameters
/// - `byte_order`: Byte order used by the length prefix.
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_u32(&mut self, byte_order: ByteOrder, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a big-endian `u32` byte-length prefix.
///
/// # Parameters
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_u32_be(&mut self, max_len: usize) -> Result<String>;
/// Reads a UTF-8 string with a little-endian `u32` byte-length prefix.
///
/// # Parameters
/// - `max_len`: Maximum accepted UTF-8 payload length in bytes.
///
/// # Returns
/// The decoded string.
///
/// # Errors
/// Returns an I/O error for length or payload reads, [`std::io::ErrorKind::InvalidData`]
/// when the encoded length exceeds `max_len`, or [`std::io::ErrorKind::InvalidData`]
/// when the payload is not valid UTF-8.
fn read_utf8_string_u32_le(&mut self, max_len: usize) -> Result<String>;
}
impl<T> StringReadExt for T
where
T: Read + ?Sized,
{
#[inline]
fn read_utf8_payload(&mut self, len: usize, max_len: usize) -> Result<String> {
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_uleb(&mut self, max_len: usize) -> Result<String> {
let len = self.read_uleb_usize()?;
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_uleb_strict(&mut self, max_len: usize) -> Result<String> {
let len = self.read_uleb_usize_strict()?;
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_u16(&mut self, byte_order: ByteOrder, max_len: usize) -> Result<String> {
let len = usize::from(self.read_u16(byte_order)?);
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_u16_be(&mut self, max_len: usize) -> Result<String> {
let len = self.read_u16_be()? as usize;
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_u16_le(&mut self, max_len: usize) -> Result<String> {
let len = self.read_u16_le()? as usize;
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_u32(&mut self, byte_order: ByteOrder, max_len: usize) -> Result<String> {
let len = self.read_u32(byte_order)? as usize;
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_u32_be(&mut self, max_len: usize) -> Result<String> {
let len = self.read_u32_be()? as usize;
read_utf8_payload_impl(self, len, max_len)
}
#[inline]
fn read_utf8_string_u32_le(&mut self, max_len: usize) -> Result<String> {
let len = self.read_u32_le()? as usize;
read_utf8_payload_impl(self, len, max_len)
}
}