56 lines
1.5 KiB
Rust
56 lines
1.5 KiB
Rust
//! Macintosh archived format header utilities.
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use crate::durandal::bin::*;
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/// Checks for an AppleSingle header. Returns offset to the resource fork.
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pub fn check_apple_single(b: &[u8]) -> Option<usize>
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{
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// check magic numbers
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if b[0..8] != [0, 5, 22, 0, 0, 2, 0, 0] {return None;}
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// get the resource fork (entity 1)
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let num = b.o_u16b(24)? as usize;
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for i in 0..num {
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let p = 26 + 12 * i;
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let ent = b.o_u32b(p )?;
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let ofs = b.o_u32b(p+4)? as usize;
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let len = b.o_u32b(p+8)? as usize;
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if ent == 1 {return if ofs + len > b.len() {None} else {Some(ofs)};}
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}
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// no resource fork
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None
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}
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/// Checks for a MacBinary II header. Returns offset to the resource fork.
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pub fn check_macbin(b: &[u8]) -> Option<usize>
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{
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// check legacy version, length, zero fill, and macbin2 version
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if b[0] != 0 || b[1] > 63 || b[74] != 0 || b[123] > 129 {return None;}
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let mut crc = 0;
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// check header crc
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for i in 0..124 {
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for j in 8..16 {
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let d = b[i] as (u16) << j;
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if (d ^ crc) & 0x8000 != 0 {crc = crc << 1 ^ 0x1021;}
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else {crc <<= 1;}
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}
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}
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// if ok, resource fork follows
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if crc == b.o_u16b(124)? {Some(128)} else {None}
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}
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/// Reads a MacBin or AppleSingle header if there is one and returns the
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/// offset from the start of the header to the resource fork (if one is found.)
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pub fn try_mac_header(b: &[u8]) -> usize
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{
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if let Some(ofs) = check_macbin(b) {ofs}
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else {check_apple_single(b).unwrap_or(0)}
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}
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// EOF
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