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-rw-r--r--src/port/tar.c206
1 files changed, 206 insertions, 0 deletions
diff --git a/src/port/tar.c b/src/port/tar.c
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--- /dev/null
+++ b/src/port/tar.c
@@ -0,0 +1,206 @@
+#include "c.h"
+
+#include <sys/stat.h>
+
+#include "pgtar.h"
+
+/*
+ * Print a numeric field in a tar header. The field starts at *s and is of
+ * length len; val is the value to be written.
+ *
+ * Per POSIX, the way to write a number is in octal with leading zeroes and
+ * one trailing space (or NUL, but we use space) at the end of the specified
+ * field width.
+ *
+ * However, the given value may not fit in the available space in octal form.
+ * If that's true, we use the GNU extension of writing \200 followed by the
+ * number in base-256 form (ie, stored in binary MSB-first). (Note: here we
+ * support only non-negative numbers, so we don't worry about the GNU rules
+ * for handling negative numbers.)
+ */
+void
+print_tar_number(char *s, int len, uint64 val)
+{
+ if (val < (((uint64) 1) << ((len - 1) * 3)))
+ {
+ /* Use octal with trailing space */
+ s[--len] = ' ';
+ while (len)
+ {
+ s[--len] = (val & 7) + '0';
+ val >>= 3;
+ }
+ }
+ else
+ {
+ /* Use base-256 with leading \200 */
+ s[0] = '\200';
+ while (len > 1)
+ {
+ s[--len] = (val & 255);
+ val >>= 8;
+ }
+ }
+}
+
+
+/*
+ * Read a numeric field in a tar header. The field starts at *s and is of
+ * length len.
+ *
+ * The POSIX-approved format for a number is octal, ending with a space or
+ * NUL. However, for values that don't fit, we recognize the GNU extension
+ * of \200 followed by the number in base-256 form (ie, stored in binary
+ * MSB-first). (Note: here we support only non-negative numbers, so we don't
+ * worry about the GNU rules for handling negative numbers.)
+ */
+uint64
+read_tar_number(const char *s, int len)
+{
+ uint64 result = 0;
+
+ if (*s == '\200')
+ {
+ /* base-256 */
+ while (--len)
+ {
+ result <<= 8;
+ result |= (unsigned char) (*++s);
+ }
+ }
+ else
+ {
+ /* octal */
+ while (len-- && *s >= '0' && *s <= '7')
+ {
+ result <<= 3;
+ result |= (*s - '0');
+ s++;
+ }
+ }
+ return result;
+}
+
+
+/*
+ * Calculate the tar checksum for a header. The header is assumed to always
+ * be 512 bytes, per the tar standard.
+ */
+int
+tarChecksum(char *header)
+{
+ int i,
+ sum;
+
+ /*
+ * Per POSIX, the checksum is the simple sum of all bytes in the header,
+ * treating the bytes as unsigned, and treating the checksum field (at
+ * offset 148) as though it contained 8 spaces.
+ */
+ sum = 8 * ' '; /* presumed value for checksum field */
+ for (i = 0; i < 512; i++)
+ if (i < 148 || i >= 156)
+ sum += 0xFF & header[i];
+ return sum;
+}
+
+
+/*
+ * Fill in the buffer pointed to by h with a tar format header. This buffer
+ * must always have space for 512 characters, which is a requirement of
+ * the tar format.
+ */
+enum tarError
+tarCreateHeader(char *h, const char *filename, const char *linktarget,
+ pgoff_t size, mode_t mode, uid_t uid, gid_t gid, time_t mtime)
+{
+ if (strlen(filename) > 99)
+ return TAR_NAME_TOO_LONG;
+
+ if (linktarget && strlen(linktarget) > 99)
+ return TAR_SYMLINK_TOO_LONG;
+
+ memset(h, 0, 512); /* assume tar header size */
+
+ /* Name 100 */
+ strlcpy(&h[0], filename, 100);
+ if (linktarget != NULL || S_ISDIR(mode))
+ {
+ /*
+ * We only support symbolic links to directories, and this is
+ * indicated in the tar format by adding a slash at the end of the
+ * name, the same as for regular directories.
+ */
+ int flen = strlen(filename);
+
+ flen = Min(flen, 99);
+ h[flen] = '/';
+ h[flen + 1] = '\0';
+ }
+
+ /* Mode 8 - this doesn't include the file type bits (S_IFMT) */
+ print_tar_number(&h[100], 8, (mode & 07777));
+
+ /* User ID 8 */
+ print_tar_number(&h[108], 8, uid);
+
+ /* Group 8 */
+ print_tar_number(&h[116], 8, gid);
+
+ /* File size 12 */
+ if (linktarget != NULL || S_ISDIR(mode))
+ /* Symbolic link or directory has size zero */
+ print_tar_number(&h[124], 12, 0);
+ else
+ print_tar_number(&h[124], 12, size);
+
+ /* Mod Time 12 */
+ print_tar_number(&h[136], 12, mtime);
+
+ /* Checksum 8 cannot be calculated until we've filled all other fields */
+
+ if (linktarget != NULL)
+ {
+ /* Type - Symbolic link */
+ h[156] = '2';
+ /* Link Name 100 */
+ strlcpy(&h[157], linktarget, 100);
+ }
+ else if (S_ISDIR(mode))
+ {
+ /* Type - directory */
+ h[156] = '5';
+ }
+ else
+ {
+ /* Type - regular file */
+ h[156] = '0';
+ }
+
+ /* Magic 6 */
+ strcpy(&h[257], "ustar");
+
+ /* Version 2 */
+ memcpy(&h[263], "00", 2);
+
+ /* User 32 */
+ /* XXX: Do we need to care about setting correct username? */
+ strlcpy(&h[265], "postgres", 32);
+
+ /* Group 32 */
+ /* XXX: Do we need to care about setting correct group name? */
+ strlcpy(&h[297], "postgres", 32);
+
+ /* Major Dev 8 */
+ print_tar_number(&h[329], 8, 0);
+
+ /* Minor Dev 8 */
+ print_tar_number(&h[337], 8, 0);
+
+ /* Prefix 155 - not used, leave as nulls */
+
+ /* Finally, compute and insert the checksum */
+ print_tar_number(&h[148], 8, tarChecksum(h));
+
+ return TAR_OK;
+}