From 28d15c9aee4bb78acaf4d3d2762a505ac2e3172a Mon Sep 17 00:00:00 2001 From: Tim Kientzle Date: Tue, 17 Mar 2009 18:51:42 -0400 Subject: Our installation instructions assume you already have a tar program. This is a minimalist implementation that should allow people to bootstrap the full libarchive distribution. SVN-Revision: 780 --- contrib/untar.c | 216 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 216 insertions(+) create mode 100644 contrib/untar.c (limited to 'contrib') diff --git a/contrib/untar.c b/contrib/untar.c new file mode 100644 index 00000000..f9fcdf0a --- /dev/null +++ b/contrib/untar.c @@ -0,0 +1,216 @@ +/* + * "untar" is a minimal tar extractor. It should work with + * most ustar tar archives. It is intended to be sufficient + * to extract the distribution for a full-featured tar program. + * + * This is a single-file C program that compiles into a standalone + * executable. + * + * To compile: cc -o untar untar.c + * + * Usage: untar + * + * Written by Tim Kientzle, March 2009. + * + * Released into the public domain. + */ + +/* These are all highly standard and portable headers. */ +#include +#include +#include + +/* This is for mkdir(); this may need to be changed for some platforms. */ +#include /* For mkdir() */ + +/* Parse an octal number, ignoring leading and trailing nonsense. */ +static int +parseoct(const char *p, size_t n) +{ + int i = 0; + + while (*p < '0' || *p > '7') { + ++p; + --n; + } + while (*p >= '0' && *p <= '7' && n > 0) { + i *= 8; + i += *p - '0'; + ++p; + --n; + } + return (i); +} + +/* Returns true if this is 512 zero bytes. */ +static int +is_end_of_archive(const char *p) +{ + int n; + for (n = 512; n > 0; --n) + if (p[n] != '\0') + return (0); + return (1); +} + +/* Create a directory, including parent directories as necessary. */ +static void +create_dir(char *pathname, int mode) +{ + char *p; + int r; + + /* Strip trailing '/' */ + if (pathname[strlen(pathname) - 1] == '/') + pathname[strlen(pathname) - 1] = '\0'; + + /* Try creating the directory. */ + r = mkdir(pathname, mode); + + if (r != 0) { + /* On failure, try creating parent directory. */ + p = strrchr(pathname, '/'); + if (p != NULL) { + *p = '\0'; + create_dir(pathname, 0755); + *p = '/'; + r = mkdir(pathname, mode); + } + } + if (r != 0) + fprintf(stderr, "Could not create directory %s\n", pathname); +} + +/* Create a file, including parent directory as necessary. */ +static FILE * +create_file(char *pathname, int mode) +{ + FILE *f; + f = fopen(pathname, "w+"); + if (f == NULL) { + /* Try creating parent dir and then creating file. */ + char *p = strrchr(pathname, '/'); + if (p != NULL) { + *p = '\0'; + create_dir(pathname, 0755); + *p = '/'; + f = fopen(pathname, "w+"); + } + } + return (f); +} + +/* Verify the tar checksum. */ +static int +verify_checksum(const char *p) +{ + int n, u = 0; + for (n = 0; n < 512; ++n) { + if (n < 148 || n > 155) + /* Standard tar checksum adds unsigned bytes. */ + u += ((unsigned char *)p)[n]; + else + u += 0x20; + + } + return (u == parseoct(p + 148, 8)); +} + +/* Extract a tar archive. */ +static int +untar(FILE *a, const char *path) +{ + char buff[512]; + FILE *f = NULL; + size_t bytes_read; + int filesize; + + printf("Extracting from %s\n", path); + for (;;) { + bytes_read = fread(buff, 1, 512, a); + if (bytes_read < 512) { + fprintf(stderr, + "Short read on %s: expected 512, got %d\n", + path, bytes_read); + return; + } + if (is_end_of_archive(buff)) { + printf("End of %s\n", path); + return; + } + if (!verify_checksum(buff)) { + fprintf(stderr, "Checksum failure\n"); + return; + } + filesize = parseoct(buff + 124, 12); + switch (buff[156]) { + case '1': + printf(" Ignoring hardlink %s\n", buff); + break; + case '2': + printf(" Ignoring symlink %s\n", buff); + break; + case '3': + printf(" Ignoring character device %s\n", + buff); + break; + case '4': + printf(" Ignoring block device %s\n", buff); + break; + case '5': + printf(" Extracting dir %s\n", buff); + create_dir(buff, parseoct(buff + 100, 8)); + break; + case '6': + printf(" Ignoring FIFO %s\n", buff); + break; + default: + printf(" Extracting file %s\n", buff); + f = create_file(buff, parseoct(buff + 100, 8)); + break; + } + while (filesize > 0) { + bytes_read = fread(buff, 1, 512, a); + if (bytes_read < 512) { + fprintf(stderr, + "Short read on %s: Expected 512, got %d\n", + path, bytes_read); + return; + } + if (filesize < 512) + bytes_read = filesize; + if (f != NULL) { + if (fwrite(buff, 1, bytes_read, f) + != bytes_read) + { + fprintf(stderr, "Failed write\n"); + fclose(f); + f = NULL; + } + } + filesize -= bytes_read; + } + if (f != NULL) { + fclose(f); + f = NULL; + } + } +} + +int +main(int argc, char **argv) +{ + FILE *a; + + ++argv; /* Skip program name */ + for ( ;*argv != NULL; ++argv) { + a = fopen(*argv, "r"); + if (a == NULL) + fprintf(stderr, "Unable to open %s\n", *argv); + else { + untar(a, *argv); + fclose(a); + } + } + return (0); +} -- cgit v1.2.1