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Generate ZIP files the same way as Windows

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This commit is contained in:
Justine Tunney 2021-03-01 06:24:11 -08:00
parent d932948fb4
commit f4298f10c2
11 changed files with 112 additions and 43 deletions
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38
libc/str/zipfindcentraldir.c
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@ -18,16 +18,34 @@
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/zip.h"
uint8_t *zipfindcentraldir(const uint8_t *map, size_t mapsize) {
const uint8_t *p, *pe;
for (p = map + mapsize - kZipCdirHdrMinSize,
pe = mapsize > 65536 + kZipCdirHdrMinSize
? map + mapsize - 65536 - kZipCdirHdrMinSize
: map;
p >= pe; --p) {
if (ZIP_CDIR_MAGIC(p) == kZipCdirHdrMagic) {
return (/*unconst*/ uint8_t *)p;
}
/**
* Locates End Of Central Directory record in ZIP file.
*
* We search backwards for the End Of Central Directory Record magnum.
* The ZIP spec says this can be anywhere in the last 64kb. We go all
* the way since .com.dbg binaries will have lots of DWARF stuff after
* the embedded .com binary. As such, we sanity check the other fields
* too to make sure the record seems legit and it's not just a random
* occurrence of the magnum.
*
* @param p points to file memory
* @param n is byte size of file
*/
uint8_t *zipfindcentraldir(const uint8_t *p, size_t n) {
size_t i;
if (n >= kZipCdirHdrMinSize) {
i = n - kZipCdirHdrMinSize;
do {
if (ZIP_CDIR_MAGIC(p + i) == kZipCdirHdrMagic &&
i + ZIP_CDIR_HDRSIZE(p + i) <= n &&
ZIP_CDIR_DISK(p + i) == ZIP_CDIR_STARTINGDISK(p + i) &&
ZIP_CDIR_RECORDSONDISK(p + i) == ZIP_CDIR_RECORDS(p + i) &&
ZIP_CDIR_RECORDS(p + i) * kZipCdirHdrMinSize <=
ZIP_CDIR_SIZE(p + i) &&
ZIP_CDIR_OFFSET(p + i) + ZIP_CDIR_SIZE(p + i) <= i) {
return (/*unconst*/ uint8_t *)(p + i);
}
} while (i--);
}
return NULL;
}