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Add filesystem index to ZipOS

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This change brings the /zip/... read-only filesystem into performance
parity with the native Linux filesystem which doesn't use compression
therefore, imagine how much faster this could be with bloom filtering
rather than simple binary search, and if we used zstd instead of zlib
This commit is contained in:
Justine Tunney 2023-08-18 07:04:55 -07:00
parent 7100b1cf91
commit 5b42c810a5
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GPG key ID: BE714B4575D6E328
7 changed files with 93 additions and 25 deletions
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61
libc/runtime/zipos-find.c
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@ -16,37 +16,66 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/macros.internal.h"
#include "libc/runtime/zipos.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/s.h"
#include "libc/sysv/errfuns.h"
#include "libc/zip.internal.h"
static ssize_t __zipos_scan(struct Zipos *zipos, struct ZiposUri *name) {
size_t len = name->len;
ssize_t __zipos_scan(struct Zipos *zipos, struct ZiposUri *name) {
// strip trailing slash from search name
int len = name->len;
if (len && name->path[len - 1] == '/') {
--len;
}
// empty string means the /zip root directory
if (!len) {
return ZIPOS_SYNTHETIC_DIRECTORY;
}
bool found_subfile = false;
size_t c = GetZipCdirOffset(zipos->cdir);
size_t n = GetZipCdirRecords(zipos->cdir);
for (size_t i = 0; i < n; ++i, c += ZIP_CFILE_HDRSIZE(zipos->map + c)) {
const char *zname = ZIP_CFILE_NAME(zipos->map + c);
size_t zsize = ZIP_CFILE_NAMESIZE(zipos->map + c);
if ((len == zsize || (len + 1 == zsize && zname[len] == '/')) &&
!memcmp(name->path, zname, len)) {
return c;
} else if (len + 1 < zsize && zname[len] == '/' &&
!memcmp(name->path, zname, len)) {
found_subfile = true;
// binary search for leftmost name in central directory
int l = 0;
int r = zipos->records;
while (l < r) {
int m = (l & r) + ((l ^ r) >> 1); // floor((a+b)/2)
const char *xp = ZIP_CFILE_NAME(zipos->map + zipos->index[m]);
const char *yp = name->path;
int xn = ZIP_CFILE_NAMESIZE(zipos->map + zipos->index[m]);
int yn = len;
int n = MIN(xn, yn);
int c;
if (n) {
if (!(c = memcmp(xp, yp, n))) {
c = xn - yn; // xn and yn are 16-bit
}
} else {
c = xn - yn;
}
if (c < 0) {
l = m + 1;
} else {
r = m;
}
}
if (found_subfile) {
return ZIPOS_SYNTHETIC_DIRECTORY;
// return pointer to leftmost record if it matches
if (l < zipos->records) {
size_t cfile = zipos->index[l];
const char *zname = ZIP_CFILE_NAME(zipos->map + cfile);
int zsize = ZIP_CFILE_NAMESIZE(zipos->map + cfile);
if ((len == zsize || (len + 1 == zsize && zname[len] == '/')) &&
!memcmp(name->path, zname, len)) {
return cfile;
} else if (len + 1 < zsize && zname[len] == '/' &&
!memcmp(name->path, zname, len)) {
return ZIPOS_SYNTHETIC_DIRECTORY;
}
}
// otherwise return not found
return -1;
}