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#include <init/stdlib.h>
#include <shared/flags.h>
#include <shared/syscalls.h>
#include <stdint.h>
#define BUF_SIZE 64
static int tar_open(const char *path, int len, void *base, size_t base_len);
static int tar_read(struct fs_wait_response *res);
static int tar_size(void *sector);
static void *tar_find(const char *path, size_t path_len, void *base, size_t base_len);
static int oct_parse(char *str, size_t len);
void tar_driver(void *base) {
static char buf[BUF_SIZE];
struct fs_wait_response res;
for (;;) {
switch (_syscall_fs_wait(buf, BUF_SIZE, &res)) {
case VFSOP_OPEN:
_syscall_fs_respond(NULL, tar_open(buf, res.len, base, ~0));
break;
case VFSOP_READ:
tar_read(&res);
break;
default:
_syscall_fs_respond(NULL, -1); // unsupported
break;
}
}
}
static int tar_open(const char *path, int len, void *base, size_t base_len) {
void *ptr;
if (len <= 1) return -1;
path += 1; // skip the leading slash
len -= 1;
ptr = tar_find(path, len, base, ~0);
if (!ptr) return -1;
return (int)ptr;
}
static int tar_read(struct fs_wait_response *res) {
void *meta = (void*)res->id;
char type = *(char*)(meta + 156);
switch (type) {
case '\0':
case '0': { /* normal files */
int size = tar_size(meta);
if (res->offset < 0 || res->offset > size) {
// TODO support negative offsets
_syscall_fs_respond(NULL, -1);
} else {
_syscall_fs_respond(meta + 512 + res->offset, size - res->offset);
}
break;
}
case '5': /* directory */
_syscall_fs_respond("[directory]", 11);
break;
default:
_syscall_fs_respond(NULL, -1);
break;
}
}
static int tar_size(void *sector) {
return oct_parse(sector + 124, 11);
}
static void *tar_find(const char *path, size_t path_len, void *base, size_t base_len) {
int size;
if (path_len > 100) return NULL; // illegal path
for (size_t off = 0; off < base_len;) {
if (0 != memcmp(base + off + 257, "ustar", 5))
break; // not a metadata sector
if (0 == memcmp(base + off, path, path_len) &&
*(char*)(base + off + path_len) == '\0')
return base + off; // file found, quit
size = tar_size(base + off);
off += 512; // skip this metadata sector
off += (size + 511) & ~511; // skip the data sectors
}
return NULL;
}
static int oct_parse(char *str, size_t len) {
int res = 0;
for (size_t i = 0; i < len; i++) {
res *= 8;
res += str[i] - '0'; // no format checking
}
return res;
}
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