Marc-André Lemburg | e5006eb | 2001-07-31 13:24:44 +0000 | [diff] [blame] | 1 | #include "Python.h" |
Marc-André Lemburg | e5006eb | 2001-07-31 13:24:44 +0000 | [diff] [blame] | 2 | |
Victor Stinner | e822e37 | 2020-06-15 21:59:47 +0200 | [diff] [blame] | 3 | /* snprintf() and vsnprintf() wrappers. |
| 4 | |
| 5 | If the platform has vsnprintf, we use it, else we |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 6 | emulate it in a half-hearted way. Even if the platform has it, we wrap |
| 7 | it because platforms differ in what vsnprintf does in case the buffer |
| 8 | is too small: C99 behavior is to return the number of characters that |
| 9 | would have been written had the buffer not been too small, and to set |
| 10 | the last byte of the buffer to \0. At least MS _vsnprintf returns a |
| 11 | negative value instead, and fills the entire buffer with non-\0 data. |
| 12 | |
| 13 | The wrappers ensure that str[size-1] is always \0 upon return. |
| 14 | |
| 15 | PyOS_snprintf and PyOS_vsnprintf never write more than size bytes |
| 16 | (including the trailing '\0') into str. |
| 17 | |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 18 | Return value (rv): |
| 19 | |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 20 | When 0 <= rv < size, the output conversion was unexceptional, and |
| 21 | rv characters were written to str (excluding a trailing \0 byte at |
| 22 | str[rv]). |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 23 | |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 24 | When rv >= size, output conversion was truncated, and a buffer of |
| 25 | size rv+1 would have been needed to avoid truncation. str[size-1] |
| 26 | is \0 in this case. |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 27 | |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 28 | When rv < 0, "something bad happened". str[size-1] is \0 in this |
| 29 | case too, but the rest of str is unreliable. It could be that |
| 30 | an error in format codes was detected by libc, or on platforms |
| 31 | with a non-C99 vsnprintf simply that the buffer wasn't big enough |
| 32 | to avoid truncation, or on platforms without any vsnprintf that |
| 33 | PyMem_Malloc couldn't obtain space for a temp buffer. |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 34 | |
| 35 | CAUTION: Unlike C99, str != NULL and size > 0 are required. |
Victor Stinner | 7ab92d5 | 2020-06-16 00:54:44 +0200 | [diff] [blame] | 36 | Also, size must be smaller than INT_MAX. |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 37 | */ |
| 38 | |
| 39 | int |
| 40 | PyOS_snprintf(char *str, size_t size, const char *format, ...) |
| 41 | { |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 42 | int rc; |
| 43 | va_list va; |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 44 | |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 45 | va_start(va, format); |
| 46 | rc = PyOS_vsnprintf(str, size, format, va); |
| 47 | va_end(va); |
| 48 | return rc; |
Tim Peters | faad5ad | 2001-12-03 00:43:33 +0000 | [diff] [blame] | 49 | } |
| 50 | |
| 51 | int |
| 52 | PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va) |
| 53 | { |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 54 | assert(str != NULL); |
| 55 | assert(size > 0); |
Victor Stinner | 7ab92d5 | 2020-06-16 00:54:44 +0200 | [diff] [blame] | 56 | assert(size <= (INT_MAX - 1)); |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 57 | assert(format != NULL); |
Victor Stinner | e822e37 | 2020-06-15 21:59:47 +0200 | [diff] [blame] | 58 | |
| 59 | int len; /* # bytes written, excluding \0 */ |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 60 | /* We take a size_t as input but return an int. Sanity check |
| 61 | * our input so that it won't cause an overflow in the |
Victor Stinner | 7ab92d5 | 2020-06-16 00:54:44 +0200 | [diff] [blame] | 62 | * vsnprintf return value. */ |
| 63 | if (size > INT_MAX - 1) { |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 64 | len = -666; |
| 65 | goto Done; |
| 66 | } |
Marc-André Lemburg | e5006eb | 2001-07-31 13:24:44 +0000 | [diff] [blame] | 67 | |
Victor Stinner | e822e37 | 2020-06-15 21:59:47 +0200 | [diff] [blame] | 68 | #if defined(_MSC_VER) |
| 69 | len = _vsnprintf(str, size, format, va); |
Marc-André Lemburg | e5006eb | 2001-07-31 13:24:44 +0000 | [diff] [blame] | 70 | #else |
Victor Stinner | 7ab92d5 | 2020-06-16 00:54:44 +0200 | [diff] [blame] | 71 | len = vsnprintf(str, size, format, va); |
Marc-André Lemburg | e5006eb | 2001-07-31 13:24:44 +0000 | [diff] [blame] | 72 | #endif |
Victor Stinner | e822e37 | 2020-06-15 21:59:47 +0200 | [diff] [blame] | 73 | |
Georg Brandl | f78e02b | 2008-06-10 17:40:04 +0000 | [diff] [blame] | 74 | Done: |
Victor Stinner | e822e37 | 2020-06-15 21:59:47 +0200 | [diff] [blame] | 75 | if (size > 0) { |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 76 | str[size-1] = '\0'; |
Victor Stinner | e822e37 | 2020-06-15 21:59:47 +0200 | [diff] [blame] | 77 | } |
Antoine Pitrou | f95a1b3 | 2010-05-09 15:52:27 +0000 | [diff] [blame] | 78 | return len; |
Marc-André Lemburg | e5006eb | 2001-07-31 13:24:44 +0000 | [diff] [blame] | 79 | } |