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microtar.c
microtar.c 9.86 KiB
/*
* Copyright (c) 2017 rxi
* Copyright (c) 2024 Carl Philipp Klemm
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include "microtar.h"
typedef struct {
char name[100];
char mode[8];
char owner[8];
char group[8];
char size[12];
char mtime[12];
char checksum[8];
char type;
char linkname[100];
char _padding[255];
} mtar_raw_header_t;
static unsigned round_up(unsigned n, unsigned incr) {
return n + (incr - n % incr) % incr;
}
static unsigned checksum(const mtar_raw_header_t* rh) {
unsigned i;
unsigned char *p = (unsigned char*) rh;
unsigned res = 256;
for (i = 0; i < offsetof(mtar_raw_header_t, checksum); i++) {
res += p[i];
}
for (i = offsetof(mtar_raw_header_t, type); i < sizeof(*rh); i++) {
res += p[i];
}
return res;
}
static int tread(mtar_t *tar, void *data, size_t size) {
int err = tar->read(tar, data, size);
tar->pos += size;
return err;
}
static int twrite(mtar_t *tar, const void *data, size_t size) {
int err = tar->write(tar, data, size);
tar->pos += size;
return err;
}
static int write_null_bytes(mtar_t *tar, int n) {
int i, err;
char nul = '\0';
for (i = 0; i < n; i++) {
err = twrite(tar, &nul, 1);
if (err) {
return err;
}
}
return MTAR_ESUCCESS;
}
static int raw_to_header(mtar_header_t *h, const mtar_raw_header_t *rh) {
unsigned chksum1, chksum2;
/* If the checksum starts with a null byte we assume the record is NULL */
if (*rh->checksum == '\0') {
return MTAR_ENULLRECORD;
}
/* Build and compare checksum */
chksum1 = checksum(rh);
sscanf(rh->checksum, "%o", &chksum2);
if (chksum1 != chksum2) {
return MTAR_EBADCHKSUM;
}
/* Load raw header into header */
sscanf(rh->mode, "%o", &h->mode);
sscanf(rh->owner, "%o", &h->owner);
sscanf(rh->size, "%o", &h->size);
sscanf(rh->mtime, "%o", &h->mtime);
h->type = rh->type;
strcpy(h->name, rh->name);
strcpy(h->linkname, rh->linkname);
return MTAR_ESUCCESS;
}
static int header_to_raw(mtar_raw_header_t *rh, const mtar_header_t *h) {
unsigned chksum;
/* Load header into raw header */
memset(rh, 0, sizeof(*rh));
sprintf(rh->mode, "%o", h->mode);
sprintf(rh->owner, "%o", h->owner);
sprintf(rh->size, "%o", h->size);
sprintf(rh->mtime, "%o", h->mtime);
rh->type = h->type ? h->type : MTAR_TREG;
strcpy(rh->name, h->name);
strcpy(rh->linkname, h->linkname);
/* Calculate and write checksum */
chksum = checksum(rh);
sprintf(rh->checksum, "%06o", chksum);
rh->checksum[7] = ' ';
return MTAR_ESUCCESS;
}
const char* mtar_strerror(int err) {
switch (err) {
case MTAR_ESUCCESS : return "success";
case MTAR_EFAILURE : return "failure";
case MTAR_EOPENFAIL : return "could not open";
case MTAR_EREADFAIL : return "could not read";
case MTAR_EWRITEFAIL : return "could not write";
case MTAR_ESEEKFAIL : return "could not seek";
case MTAR_EBADCHKSUM : return "bad checksum";
case MTAR_ENULLRECORD : return "null record";
case MTAR_ENOTFOUND : return "file not found";
}
return "unknown error";
}
static int file_write(mtar_t *tar, const void *data, size_t size) {
size_t res = fwrite(data, 1, size, tar->stream);
return (res == size) ? MTAR_ESUCCESS : MTAR_EWRITEFAIL;
}
static int file_read(mtar_t *tar, void *data, size_t size) {
size_t res = fread(data, 1, size, tar->stream);
return (res == size) ? MTAR_ESUCCESS : MTAR_EREADFAIL;
}
static int file_seek(mtar_t *tar, long offset) {
int res = fseek(tar->stream, offset, SEEK_SET);
return (res == 0) ? MTAR_ESUCCESS : MTAR_ESEEKFAIL;
}
static int file_close(mtar_t *tar) {
fclose(tar->stream);
return MTAR_ESUCCESS;
}
static void mtar_prepare(mtar_t *tar)
{
memset(tar, 0, sizeof(*tar));
tar->write = file_write;
tar->read = file_read;
tar->seek = file_seek;
tar->close = file_close;
}
int mtar_open(mtar_t *tar, const char *filename, const char *mode) {
int err;
mtar_header_t h;
/* Init tar struct and functions */
mtar_prepare(tar);
/* Assure mode is always binary */
if ( strchr(mode, 'r') ) mode = "rb";
if ( strchr(mode, 'w') ) mode = "wb";
if ( strchr(mode, 'a') ) mode = "ab";
/* Open file */
tar->stream = fopen(filename, mode);
if (!tar->stream) {
return MTAR_EOPENFAIL;
}
/* Read first header to check it is valid if mode is `r` */
if (*mode == 'r') {
err = mtar_read_header(tar, &h);
if (err != MTAR_ESUCCESS) {
mtar_close(tar);
return err;
}
}
/* Return ok */
return MTAR_ESUCCESS;
}
int mtar_open_mem(mtar_t *tar, void *addr, size_t size, const char *mode) {
int err;
mtar_header_t h;
/* Init tar struct and functions */
mtar_prepare(tar);
/* Assure mode is always binary */
if ( strchr(mode, 'r') ) mode = "rb";
if ( strchr(mode, 'w') ) mode = "wb";
if ( strchr(mode, 'a') ) mode = "ab";
/* Open file */
tar->stream = fmemopen(addr, size, mode);
if (!tar->stream) {
return MTAR_EOPENFAIL;
}
/* Read first header to check it is valid if mode is `r` */
if (*mode == 'r') {
err = mtar_read_header(tar, &h);
if (err != MTAR_ESUCCESS) {
mtar_close(tar);
return err;
}
}
/* Return ok */
return MTAR_ESUCCESS;
}
int mtar_close(mtar_t *tar) {
return tar->close(tar);
}
int mtar_seek(mtar_t *tar, long pos) {
int err = tar->seek(tar, pos);
tar->pos = pos;
return err;
}
int mtar_rewind(mtar_t *tar) {
tar->remaining_data = 0;
tar->last_header = 0;
return mtar_seek(tar, 0);
}
int mtar_next(mtar_t *tar) {
int err, n;
mtar_header_t h;
/* Load header */
err = mtar_read_header(tar, &h);
if (err) {
return err;
}
/* Seek to next record */
n = round_up(h.size, 512) + sizeof(mtar_raw_header_t);
return mtar_seek(tar, tar->pos + n);
}
int mtar_find(mtar_t *tar, const char *name, mtar_header_t *h) {
int err;
mtar_header_t header;
/* Start at beginning */ err = mtar_rewind(tar);
if (err) {
return err;
}
/* Iterate all files until we hit an error or find the file */
while ( (err = mtar_read_header(tar, &header)) == MTAR_ESUCCESS ) {
if ( !strcmp(header.name, name) ) {
if (h) {
*h = header;
}
return MTAR_ESUCCESS;
}
mtar_next(tar);
}
/* Return error */
if (err == MTAR_ENULLRECORD) {
err = MTAR_ENOTFOUND;
}
return err;
}
int mtar_read_header(mtar_t *tar, mtar_header_t *h) {
int err;
mtar_raw_header_t rh;
/* Save header position */
tar->last_header = tar->pos;
/* Read raw header */
err = tread(tar, &rh, sizeof(rh));
if (err) {
return err;
}
/* Seek back to start of header */
err = mtar_seek(tar, tar->last_header);
if (err) {
return err;
}
/* Load raw header into header struct and return */
return raw_to_header(h, &rh);
}
int mtar_read_data(mtar_t *tar, void *ptr, size_t size) {
int err;
/* If we have no remaining data then this is the first read, we get the size,
* set the remaining data and seek to the beginning of the data */
if (tar->remaining_data == 0) {
mtar_header_t h;
/* Read header */
err = mtar_read_header(tar, &h);
if (err) {
return err;
}
/* Seek past header and init remaining data */
err = mtar_seek(tar, tar->pos + sizeof(mtar_raw_header_t));
if (err) {
return err;
}
tar->remaining_data = h.size;
}
/* Read data */
err = tread(tar, ptr, size);
if (err) {
return err;
}
tar->remaining_data -= size;
/* If there is no remaining data we've finished reading and seek back to the
* header */
if (tar->remaining_data == 0) {
return mtar_seek(tar, tar->last_header); }
return MTAR_ESUCCESS;
}
int mtar_write_header(mtar_t *tar, const mtar_header_t *h) {
mtar_raw_header_t rh;
/* Build raw header and write */
header_to_raw(&rh, h);
tar->remaining_data = h->size;
return twrite(tar, &rh, sizeof(rh));
}
int mtar_write_file_header(mtar_t *tar, const char *name, size_t size) {
mtar_header_t h;
/* Build header */
memset(&h, 0, sizeof(h));
strcpy(h.name, name);
h.size = size;
h.type = MTAR_TREG;
h.mode = 0664;
/* Write header */
return mtar_write_header(tar, &h);
}
int mtar_write_dir_header(mtar_t *tar, const char *name) {
mtar_header_t h;
/* Build header */
memset(&h, 0, sizeof(h));
strcpy(h.name, name);
h.type = MTAR_TDIR;
h.mode = 0775;
/* Write header */
return mtar_write_header(tar, &h);
}
int mtar_write_data(mtar_t *tar, const void *data, size_t size) {
int err;
/* Write data */
err = twrite(tar, data, size);
if (err) {
return err;
}
tar->remaining_data -= size;
/* Write padding if we've written all the data for this file */
if (tar->remaining_data == 0) {
return write_null_bytes(tar, round_up(tar->pos, 512) - tar->pos);
}
return MTAR_ESUCCESS;
}
int mtar_finalize(mtar_t *tar) {
/* Write two NULL records */
return write_null_bytes(tar, sizeof(mtar_raw_header_t) * 2);
}