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Lightly refactor and test format_hex_number_sigsafe

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Better tests for upper bounds, and for failing cases.

Also, change the function's interface to take a buffer length rather
than a maximum length, and then NUL-terminate: functions that don't
NUL-terminate are trouble waiting to happen.
This commit is contained in:
Nick Mathewson 2013-07-15 12:52:29 -04:00
parent 18136afbbb
commit 9fda7e8cd1
2 changed files with 21 additions and 13 deletions
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20
src/common/util.c
View File

@ -3382,13 +3382,13 @@ tor_join_win_cmdline(const char *argv[])
} }
/** /**
* Helper function to output hex numbers, called by * Helper function to output hex numbers from within a signal handler.
* format_helper_exit_status(). This writes the hexadecimal digits of x into
* buf, up to max_len digits, and returns the actual number of digits written.
* If there is insufficient space, it will write nothing and return 0.
* *
* This function DOES NOT add a terminating NUL character to its output: be * Writes the nul-terminated hexadecimal digits of <b>x</b> into a buffer
* careful! * <b>buf</b> of size <b>buf_len</b>, and return the actual number of digits
* written, not counting the terminal NUL.
*
* If there is insufficient space, write nothing and return 0.
* *
* This accepts an unsigned int because format_helper_exit_status() needs to * This accepts an unsigned int because format_helper_exit_status() needs to
* call it with a signed int and an unsigned char, and since the C standard * call it with a signed int and an unsigned char, and since the C standard
@ -3403,14 +3403,14 @@ tor_join_win_cmdline(const char *argv[])
* arbitrary C functions. * arbitrary C functions.
*/ */
int int
format_hex_number_sigsafe(unsigned int x, char *buf, int max_len) format_hex_number_sigsafe(unsigned int x, char *buf, int buf_len)
{ {
int len; int len;
unsigned int tmp; unsigned int tmp;
char *cur; char *cur;
/* Sanity check */ /* Sanity check */
if (!buf || max_len <= 0) if (!buf || buf_len <= 1)
return 0; return 0;
/* How many chars do we need for x? */ /* How many chars do we need for x? */
@ -3426,7 +3426,7 @@ format_hex_number_sigsafe(unsigned int x, char *buf, int max_len)
} }
/* Bail if we would go past the end of the buffer */ /* Bail if we would go past the end of the buffer */
if (len > max_len) if (len+1 > buf_len)
return 0; return 0;
/* Point to last one */ /* Point to last one */
@ -3438,6 +3438,8 @@ format_hex_number_sigsafe(unsigned int x, char *buf, int max_len)
x >>= 4; x >>= 4;
} while (x != 0 && cur >= buf); } while (x != 0 && cur >= buf);
buf[len] = '\0';
/* Return len */ /* Return len */
return len; return len;
} }

14
src/test/test_util.c
View File

@ -2643,7 +2643,8 @@ test_util_format_hex_number(void *ptr)
{"1", 1}, {"1", 1},
{"273A", 0x273a}, {"273A", 0x273a},
{"FFFF", 0xffff}, {"FFFF", 0xffff},
{"7FFFFFFF", 0x7fffffff},
{"FFFFFFFF", 0xffffffff},
#if UINT_MAX >= 0xffffffff #if UINT_MAX >= 0xffffffff
{"31BC421D", 0x31bc421d}, {"31BC421D", 0x31bc421d},
{"FFFFFFFF", 0xffffffff}, {"FFFFFFFF", 0xffffffff},
@ -2654,18 +2655,23 @@ test_util_format_hex_number(void *ptr)
(void)ptr; (void)ptr;
for (i = 0; test_data[i].str != NULL; ++i) { for (i = 0; test_data[i].str != NULL; ++i) {
len = format_hex_number_sigsafe(test_data[i].x, buf, 32); len = format_hex_number_sigsafe(test_data[i].x, buf, sizeof(buf));
test_neq(len, 0); test_neq(len, 0);
buf[len] = '\0'; test_eq(len, strlen(buf));
test_streq(buf, test_data[i].str); test_streq(buf, test_data[i].str);
} }
test_eq(4, format_hex_number_sigsafe(0xffff, buf, 5));
test_streq(buf, "FFFF");
test_eq(0, format_hex_number_sigsafe(0xffff, buf, 4));
test_eq(0, format_hex_number_sigsafe(0, buf, 1));
done: done:
return; return;
} }
/** /**
* Test that we can properly format q Windows command line * Test that we can properly format a Windows command line
*/ */
static void static void
test_util_join_win_cmdline(void *ptr) test_util_join_win_cmdline(void *ptr)