PostgreSQL Source Code  git master
tar.c
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1 #include "c.h"
2 
3 #include <sys/stat.h>
4 
5 #include "pgtar.h"
6 
7 /*
8  * Print a numeric field in a tar header. The field starts at *s and is of
9  * length len; val is the value to be written.
10  *
11  * Per POSIX, the way to write a number is in octal with leading zeroes and
12  * one trailing space (or NUL, but we use space) at the end of the specified
13  * field width.
14  *
15  * However, the given value may not fit in the available space in octal form.
16  * If that's true, we use the GNU extension of writing \200 followed by the
17  * number in base-256 form (ie, stored in binary MSB-first). (Note: here we
18  * support only non-negative numbers, so we don't worry about the GNU rules
19  * for handling negative numbers.)
20  */
21 void
22 print_tar_number(char *s, int len, uint64 val)
23 {
24  if (val < (((uint64) 1) << ((len - 1) * 3)))
25  {
26  /* Use octal with trailing space */
27  s[--len] = ' ';
28  while (len)
29  {
30  s[--len] = (val & 7) + '0';
31  val >>= 3;
32  }
33  }
34  else
35  {
36  /* Use base-256 with leading \200 */
37  s[0] = '\200';
38  while (len > 1)
39  {
40  s[--len] = (val & 255);
41  val >>= 8;
42  }
43  }
44 }
45 
46 
47 /*
48  * Read a numeric field in a tar header. The field starts at *s and is of
49  * length len.
50  *
51  * The POSIX-approved format for a number is octal, ending with a space or
52  * NUL. However, for values that don't fit, we recognize the GNU extension
53  * of \200 followed by the number in base-256 form (ie, stored in binary
54  * MSB-first). (Note: here we support only non-negative numbers, so we don't
55  * worry about the GNU rules for handling negative numbers.)
56  */
57 uint64
58 read_tar_number(const char *s, int len)
59 {
60  uint64 result = 0;
61 
62  if (*s == '\200')
63  {
64  /* base-256 */
65  while (--len)
66  {
67  result <<= 8;
68  result |= (unsigned char) (*++s);
69  }
70  }
71  else
72  {
73  /* octal */
74  while (len-- && *s >= '0' && *s <= '7')
75  {
76  result <<= 3;
77  result |= (*s - '0');
78  s++;
79  }
80  }
81  return result;
82 }
83 
84 
85 /*
86  * Calculate the tar checksum for a header. The header is assumed to always
87  * be 512 bytes, per the tar standard.
88  */
89 int
91 {
92  int i,
93  sum;
94 
95  /*
96  * Per POSIX, the checksum is the simple sum of all bytes in the header,
97  * treating the bytes as unsigned, and treating the checksum field (at
98  * offset 148) as though it contained 8 spaces.
99  */
100  sum = 8 * ' '; /* presumed value for checksum field */
101  for (i = 0; i < 512; i++)
102  if (i < 148 || i >= 156)
103  sum += 0xFF & header[i];
104  return sum;
105 }
106 
107 
108 /*
109  * Fill in the buffer pointed to by h with a tar format header. This buffer
110  * must always have space for 512 characters, which is a requirement of
111  * the tar format.
112  */
113 enum tarError
114 tarCreateHeader(char *h, const char *filename, const char *linktarget,
115  pgoff_t size, mode_t mode, uid_t uid, gid_t gid, time_t mtime)
116 {
117  if (strlen(filename) > 99)
118  return TAR_NAME_TOO_LONG;
119 
120  if (linktarget && strlen(linktarget) > 99)
121  return TAR_SYMLINK_TOO_LONG;
122 
123  memset(h, 0, 512); /* assume tar header size */
124 
125  /* Name 100 */
126  strlcpy(&h[0], filename, 100);
127  if (linktarget != NULL || S_ISDIR(mode))
128  {
129  /*
130  * We only support symbolic links to directories, and this is
131  * indicated in the tar format by adding a slash at the end of the
132  * name, the same as for regular directories.
133  */
134  int flen = strlen(filename);
135 
136  flen = Min(flen, 99);
137  h[flen] = '/';
138  h[flen + 1] = '\0';
139  }
140 
141  /* Mode 8 - this doesn't include the file type bits (S_IFMT) */
142  print_tar_number(&h[100], 8, (mode & 07777));
143 
144  /* User ID 8 */
145  print_tar_number(&h[108], 8, uid);
146 
147  /* Group 8 */
148  print_tar_number(&h[116], 8, gid);
149 
150  /* File size 12 */
151  if (linktarget != NULL || S_ISDIR(mode))
152  /* Symbolic link or directory has size zero */
153  print_tar_number(&h[124], 12, 0);
154  else
155  print_tar_number(&h[124], 12, size);
156 
157  /* Mod Time 12 */
158  print_tar_number(&h[136], 12, mtime);
159 
160  /* Checksum 8 cannot be calculated until we've filled all other fields */
161 
162  if (linktarget != NULL)
163  {
164  /* Type - Symbolic link */
165  h[156] = '2';
166  /* Link Name 100 */
167  strlcpy(&h[157], linktarget, 100);
168  }
169  else if (S_ISDIR(mode))
170  {
171  /* Type - directory */
172  h[156] = '5';
173  }
174  else
175  {
176  /* Type - regular file */
177  h[156] = '0';
178  }
179 
180  /* Magic 6 */
181  strcpy(&h[257], "ustar");
182 
183  /* Version 2 */
184  memcpy(&h[263], "00", 2);
185 
186  /* User 32 */
187  /* XXX: Do we need to care about setting correct username? */
188  strlcpy(&h[265], "postgres", 32);
189 
190  /* Group 32 */
191  /* XXX: Do we need to care about setting correct group name? */
192  strlcpy(&h[297], "postgres", 32);
193 
194  /* Major Dev 8 */
195  print_tar_number(&h[329], 8, 0);
196 
197  /* Minor Dev 8 */
198  print_tar_number(&h[337], 8, 0);
199 
200  /* Prefix 155 - not used, leave as nulls */
201 
202  /* Finally, compute and insert the checksum */
203  print_tar_number(&h[148], 8, tarChecksum(h));
204 
205  return TAR_OK;
206 }
int tarChecksum(char *header)
Definition: tar.c:90
static PgChecksumMode mode
Definition: pg_checksums.c:61
uint64 read_tar_number(const char *s, int len)
Definition: tar.c:58
Definition: pgtar.h:17
#define Min(x, y)
Definition: c.h:920
#define pgoff_t
Definition: win32_port.h:194
tarError
Definition: pgtar.h:15
void print_tar_number(char *s, int len, uint64 val)
Definition: tar.c:22
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)
Definition: tar.c:114
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
int uid_t
Definition: win32_port.h:230
static void header(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:208
#define S_ISDIR(m)
Definition: win32_port.h:296
static char * filename
Definition: pg_dumpall.c:90
int gid_t
Definition: win32_port.h:231
int i
long val
Definition: informix.c:664