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Implement program for finding start of zip content

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Justine Tunney 2023-01-06 19:55:00 -08:00
parent b38a442386
commit 5dab97b6d4
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4 changed files with 82 additions and 5 deletions
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tool/build/zipbase.c Normal file
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#if 0
/*─────────────────────────────────────────────────────────────────╗
│ To the extent possible under law, Justine Tunney has waived │
│ all copyright and related or neighboring rights to this file, │
│ as it is written in the following disclaimers: │
│ • http://unlicense.org/ │
│ • http://creativecommons.org/publicdomain/zero/1.0/ │
╚─────────────────────────────────────────────────────────────────*/
#endif
#include "libc/calls/calls.h"
#include "libc/calls/struct/stat.h"
#include "libc/log/check.h"
#include "libc/macros.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/stdio.h"
#include "libc/sysv/consts/map.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/prot.h"
#include "libc/zip.h"
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "usage: %s FOO.COM\n", argv[0]);
fprintf(stderr,
"prints lowest file offset (in decimal bytes) at which zip\n"
"records exist within a .com, .com.dbg, or .zip file\n");
exit(1);
}
int fd = open(argv[1], O_RDONLY);
if (fd == -1) {
perror(argv[1]);
exit(1);
}
size_t n;
struct stat st;
CHECK_EQ(0, fstat(fd, &st));
n = st.st_size;
uint8_t *m;
CHECK_NE(MAP_FAILED, (m = mmap(0, n, PROT_READ, MAP_PRIVATE, fd, 0)));
uint8_t *b, *d, *p;
if ((p = FindEmbeddedApe(m, n))) {
b = p;
n -= p - m;
} else {
b = m;
}
if (!(d = GetZipCdir(b, n))) {
fprintf(stderr, "%s: couldn't locate central directory\n", argv[1]);
exit(1);
}
size_t zsize = n;
uint8_t *zmap = m;
uint8_t *zbase = b;
uint8_t *zcdir = d;
DCHECK(IsZipCdir32(zbase, zsize, zcdir - zbase) ||
IsZipCdir64(zbase, zsize, zcdir - zbase));
uint64_t cf;
uint64_t lf;
uint64_t minzipoffset;
n = GetZipCdirRecords(zcdir);
minzipoffset = cf = GetZipCdirOffset(zcdir);
for (; n--; cf += ZIP_CFILE_HDRSIZE(zbase + cf)) {
CHECK_EQ(kZipCfileHdrMagic, ZIP_CFILE_MAGIC(zbase + cf));
lf = GetZipCfileOffset(zbase + cf);
minzipoffset = MIN(minzipoffset, lf);
}
printf("%ld\n", (zbase + minzipoffset) - m);
}