ropkg/libropkg/reader.c

#include "reader.h"

#include <ropkg/reader.h>
#include <stdlib.h>
#include <string.h>

static struct ustar_header null_header = {0};

static void copy_string(
	const char *src,
	size_t src_max,
	char *dest,
	size_t dest_max)
{
	size_t start = strlen(dest);
	size_t max = b_min(size_t, src_max, dest_max - start);

	for (size_t i = 0; i < max; i++) {
		dest[start + i] = src[i];

		if (!src[i]) {
			break;
		}
	}
}

static long long from_octal(const char *s, size_t len)
{
	long at = (long)len - 2;
	long long value = 0;
	long mul = 1;
	while (at >= 0) {
		char c = s[at];
		if (c == 0 || c == ' ') {
			break;
		}

		int v = c - '0';

		value += (v * mul);
		mul *= 8;
		at--;
	}

	return value;
}

static enum ropkg_status read_file_header(struct ropkg_reader *reader)
{
	if (b_cstream_in_compressed_section(reader->r_stream)) {
		b_cstream_tx_bytes_uncompressed(
			reader->r_stream,
			&reader->r_cur_header_offset);
	} else {
		b_cstream_tx_bytes(
			reader->r_stream,
			&reader->r_cur_header_offset);
	}

	size_t nr_read = 0;
	b_status status = b_cstream_read(
		reader->r_stream,
		&reader->r_cur_header,
		sizeof reader->r_cur_header,
		&nr_read);
	if (!B_OK(status)) {
		return ROPKG_ERR_IO_FAILURE;
	}

	if (nr_read != sizeof reader->r_cur_header) {
		return ROPKG_ERR_INVALID_PKG_FILE;
	}

	memset(&reader->f_cur_file, 0x0, sizeof reader->f_cur_file);

	copy_string(
		reader->r_cur_header.tar_filename_prefix,
		sizeof reader->r_cur_header.tar_filename_prefix,
		reader->f_cur_file.f_filename,
		sizeof reader->f_cur_file.f_filename);
	copy_string(
		reader->r_cur_header.tar_filename,
		sizeof reader->r_cur_header.tar_filename,
		reader->f_cur_file.f_filename,
		sizeof reader->f_cur_file.f_filename);
	copy_string(
		reader->r_cur_header.tar_linkname,
		sizeof reader->r_cur_header.tar_linkname,
		reader->f_cur_file.f_linkname,
		sizeof reader->f_cur_file.f_linkname);

	reader->f_cur_file.f_mode = from_octal(
		reader->r_cur_header.tar_mode,
		sizeof reader->r_cur_header.tar_mode);
	reader->f_cur_file.f_uid = from_octal(
		reader->r_cur_header.tar_uid,
		sizeof reader->r_cur_header.tar_uid);
	reader->f_cur_file.f_gid = from_octal(
		reader->r_cur_header.tar_gid,
		sizeof reader->r_cur_header.tar_gid);
	reader->f_cur_file.f_filesize = from_octal(
		reader->r_cur_header.tar_filesize,
		sizeof reader->r_cur_header.tar_filesize);
	reader->f_cur_file.f_mtime = from_octal(
		reader->r_cur_header.tar_mtime,
		sizeof reader->r_cur_header.tar_mtime);
	reader->f_cur_file.f_type = reader->r_cur_header.tar_type[0];

	return ROPKG_SUCCESS;
}

enum ropkg_status ropkg_reader_open(b_cstream *fp, struct ropkg_reader **out)
{
	struct ropkg_reader *reader = malloc(sizeof *reader);
	if (!reader) {
		return ROPKG_ERR_NO_MEMORY;
	}

	memset(reader, 0x0, sizeof *reader);

	reader->r_stream = fp;

	enum ropkg_status status = read_file_header(reader);
	if (status != ROPKG_SUCCESS) {
		free(reader);
		return status;
	}

	if (!memcmp(&reader->r_cur_header, &null_header, sizeof null_header)) {
		b_cstream_skip(reader->r_stream, sizeof null_header, NULL);
		reader->r_eof = true;
	}

	*out = reader;
	return ROPKG_SUCCESS;
}

enum ropkg_status ropkg_reader_close(struct ropkg_reader *pkg)
{
	free(pkg);
	return ROPKG_SUCCESS;
}

const struct ropkg_file_info *ropkg_reader_current_file(
	struct ropkg_reader *reader)
{
	return &reader->f_cur_file;
}

enum ropkg_status ropkg_reader_move_next(struct ropkg_reader *pkg)
{
	if (pkg->r_eof) {
		return ROPKG_ERR_NO_DATA;
	}

	size_t pos = 0;
	if (b_cstream_in_compressed_section(pkg->r_stream)) {
		b_cstream_tx_bytes_uncompressed(pkg->r_stream, &pos);
	} else {
		b_cstream_tx_bytes(pkg->r_stream, &pos);
	}

	size_t end = pkg->r_cur_header_offset + sizeof pkg->r_cur_header
	           + pkg->f_cur_file.f_filesize;
	if ((end % 512) != 0) {
		end += 512 - (end % 512);
	}

	size_t skip = end - pos;

	size_t nr_skipped = 0;
	b_cstream_skip(pkg->r_stream, skip, &nr_skipped);

	if (nr_skipped != skip) {
		pkg->r_eof = true;
		return ROPKG_ERR_INVALID_PKG_FILE;
	}

	enum ropkg_status status = read_file_header(pkg);
	if (status != ROPKG_SUCCESS) {
		return status;
	}

	if (!memcmp(&pkg->r_cur_header, &null_header, sizeof null_header)) {
		b_cstream_skip(pkg->r_stream, sizeof null_header, NULL);
		pkg->r_eof = true;
	}

	return ROPKG_SUCCESS;
}

static bool compare_name(const char *target, const char *candidate)
{
	bool result = true;

	for (size_t i = 0;; i++) {
		if (target[i] == '*') {
			break;
		}

		if (target[i] != candidate[i]) {
			result = false;
			break;
		}

		if (candidate[i] == 0 || target[i] == 0) {
			break;
		}
	}

	return result;
}

enum ropkg_status ropkg_reader_move_to_file(
	struct ropkg_reader *pkg,
	const char *name)
{
	enum ropkg_status status = ROPKG_ERR_NO_ENTRY;

	while (!ropkg_reader_eof(pkg)) {
		struct ropkg_file_info *file = &pkg->f_cur_file;
		bool match = compare_name(name, file->f_filename);
		if (match) {
			return ROPKG_SUCCESS;
		}

		status = ropkg_reader_move_next(pkg);
		if (status != ROPKG_SUCCESS) {
			return status;
		}
	}

	return ROPKG_ERR_NO_ENTRY;
}

bool ropkg_reader_eof(const struct ropkg_reader *pkg)
{
	return pkg->r_eof;
}