minitar/src/util.c
apio 28085731f1 Not all 0-sized reads are errors
If you requested 0 bytes, the kernel gives you 0 bytes back
2022-11-06 14:14:06 +01:00

120 lines
3.6 KiB
C

#define _POSIX_C_SOURCE 200809L // for strndup
#define _IN_MINITAR
#include "minitar.h"
#include "tar.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>
__attribute__((weak)) noreturn void minitar_handle_panic(const char* message)
{
fprintf(stderr, "minitar: %s\n", message);
abort();
}
noreturn void minitar_panic(const char* message)
{
minitar_handle_panic(message);
}
void minitar_parse_tar_header(struct tar_header* hdr, struct minitar_entry_metadata* metadata)
{
if (!strlen(hdr->prefix))
{
strncpy(metadata->name, hdr->name, 100);
metadata->name[100] = '\0';
}
else
{
strcpy(metadata->name, hdr->prefix);
strcat(metadata->name, "/");
strncat(metadata->name, hdr->name, 100);
metadata->name[256] = '\0';
}
metadata->mode = (mode_t)strtol(hdr->mode, NULL, 8);
metadata->uid = (uid_t)strtoul(hdr->uid, NULL, 8);
metadata->gid = (gid_t)strtoul(hdr->gid, NULL, 8);
char* sizeptr = strndup(hdr->size, 12);
if (!sizeptr) minitar_panic("Failed to allocate memory to duplicate a tar header's size field");
metadata->size = (size_t)strtoull(sizeptr, NULL, 8);
free(sizeptr);
char* timeptr = strndup(hdr->mtime, 12);
if (!timeptr) minitar_panic("Failed to allocate memory to duplicate a tar header's mtime field");
metadata->mtime = (time_t)strtol(timeptr, NULL, 8);
free(timeptr);
switch (hdr->typeflag)
{
case '\0':
case '0': metadata->type = MTAR_REGULAR; break;
case '1': minitar_panic("Links to other files within a tar archive are unsupported");
case '2': minitar_panic("Symbolic links are unsupported");
case '3': metadata->type = MTAR_CHRDEV; break;
case '4': metadata->type = MTAR_BLKDEV; break;
case '5': metadata->type = MTAR_DIRECTORY; break;
case '6': minitar_panic("FIFOs are unsupported");
default: minitar_panic("Unknown entry type in tar header");
}
strcpy(metadata->uname, hdr->uname);
strcpy(metadata->gname, hdr->gname);
}
int minitar_validate_header(struct tar_header* hdr)
{
if (hdr->typeflag != '\0' && hdr->typeflag != '0' && hdr->typeflag != '1' && hdr->typeflag != '2' &&
hdr->typeflag != '3' && hdr->typeflag != '4' && hdr->typeflag != '5' && hdr->typeflag != '6')
return 0;
return !strncmp(hdr->magic, "ustar", 5);
}
int minitar_read_header(struct minitar* mp, struct tar_header* hdr)
{
size_t rc = fread(hdr, 1, sizeof *hdr, mp->stream);
if (rc == 0 && feof(mp->stream)) return 0;
if (rc == 0 && ferror(mp->stream)) minitar_panic("Error while reading file header from tar archive");
if (rc < sizeof *hdr) minitar_panic("Valid tar files should be split in 512-byte blocks");
return 1;
}
struct minitar_entry* minitar_dup_entry(struct minitar_entry* original)
{
struct minitar_entry* new = malloc(sizeof *original);
if (!new) return NULL;
memcpy(new, original, sizeof *new);
return new;
}
char* minitar_read_file(struct minitar_entry_metadata* metadata, struct minitar* mp)
{
char* buf = malloc(metadata->size + 1);
if (!buf) return NULL;
size_t nread = fread(buf, 1, metadata->size, mp->stream);
if (!nread)
{
if (feof(mp->stream))
{
free(buf);
return NULL;
}
if (ferror(mp->stream))
{
free(buf);
minitar_panic("Error while reading file data from tar archive");
}
}
else
{
long rem = 512 - (nread % 512);
fseek(mp->stream, rem, SEEK_CUR); // move the file offset over to the start of the next block
}
buf[nread] = 0;
return buf;
}