diff options
Diffstat (limited to 'src/user/app/init/driver/tar.c')
| -rw-r--r-- | src/user/app/init/driver/tar.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/src/user/app/init/driver/tar.c b/src/user/app/init/driver/tar.c new file mode 100644 index 0000000..60deccd --- /dev/null +++ b/src/user/app/init/driver/tar.c @@ -0,0 +1,158 @@ +#include <user/lib/stdlib.h> +#include <shared/flags.h> +#include <shared/syscalls.h> +#include <stdint.h> + +#define BUF_SIZE 64 + +static void *tar_open(const char *path, int len, void *base, size_t base_len); +static void tar_read(struct fs_wait_response *res, void *base, size_t base_len); +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); + + +static const char *root_fakemeta = ""; /* see comment in tar_open */ + + +void tar_driver(void *base) { + static char buf[BUF_SIZE]; + struct fs_wait_response res; + void *ptr; + while (!_syscall_fs_wait(buf, BUF_SIZE, &res)) { + switch (res.op) { + case VFSOP_OPEN: + ptr = tar_open(buf, res.len, base, ~0); + _syscall_fs_respond(ptr, ptr ? 0 : -1, 0); + break; + + case VFSOP_READ: + tar_read(&res, base, ~0); + break; + + default: + _syscall_fs_respond(NULL, -1, 0); // unsupported + break; + } + } + _syscall_exit(0); +} + +static void *tar_open(const char *path, int len, void *base, size_t base_len) { + if (len <= 0) return NULL; + path += 1; // skip the leading slash + len -= 1; + + /* TAR archives don't (seem to) contain an entry for the root dir, so i'm + * returning a fake one. this isn't a full entry because i'm currently too + * lazy to create a full one - thus, it has to be special cased in tar_read */ + if (len == 0) + return (void*)root_fakemeta; + + return tar_find(path, len, base, base_len); +} + +static void tar_read(struct fs_wait_response *res, void *base, size_t base_len) { + void *meta = (void*)res->id; + char type = *(char*)(meta + 156); + size_t meta_len; + int size; + + static char buf[BUF_SIZE]; // TODO reuse a single buffer + size_t buf_pos = 0; + + if (meta == root_fakemeta) type = '5'; /* see comment in tar_open() */ + + switch (type) { + case '\0': + case '0': /* normal files */ + size = tar_size(meta); + if (res->offset < 0 || res->offset > size) { + // TODO support negative offsets + _syscall_fs_respond(NULL, -1, 0); + } else { + _syscall_fs_respond(meta + 512 + res->offset, size - res->offset, 0); + } + break; + + case '5': /* directory */ + meta_len = strlen(meta); + size_t to_skip = res->offset; + + /* find files in dir */ + for (size_t off = 0; off < base_len;) { + if (0 != memcmp(base + off + 257, "ustar", 5)) + break; // not a metadata sector + // TODO more meaningful variable names and clean code up + + /* check if prefix matches */ + if (0 == memcmp(base + off, meta, meta_len) && + *(char*)(base + off + meta_len) != '\0') { + char *suffix = base + off + meta_len; + size_t suffix_len = strlen(suffix); + + /* check if the path contains any non-trailing slashes */ + char *next = suffix; + while (*next && *next != '/') next++; + if (*next == '/') next++; + if (*next == '\0') { + if (to_skip > suffix_len) { + to_skip -= suffix_len; + } else { + suffix += to_skip; + suffix_len -= to_skip; + to_skip = 0; + + /* it doesn't - so let's add it to the result */ + memcpy(buf + buf_pos, suffix, suffix_len); + buf[buf_pos + suffix_len] = '\0'; + buf_pos += suffix_len + 1; + // TODO no buffer overrun check + } + } + } + + size = tar_size(base + off); + off += 512; // skip this metadata sector + off += (size + 511) & ~511; // skip the data sectors + } + + _syscall_fs_respond(buf, buf_pos, 0); + break; + + default: + _syscall_fs_respond(NULL, -1, 0); + 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; +} |