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Add snprintf implementation #170

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Add snprintf implementation #170

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af03db2
feat: add snprintf
Nov 29, 2024
be3a312
fix: remove free_a
Nov 29, 2024
4db8d7e
Merge pull request #1 from icgmilk/JimHsu
icgmilk Nov 29, 2024
0db0e9c
Refactor function 'snprintf(size_t n)' to replace 'size_t' with 'int'
Dec 5, 2024
73ce0cb
Merge pull request #2 from icgmilk/JimHsu
icgmilk Dec 5, 2024
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65 changes: 65 additions & 0 deletions lib/c.c
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Original file line number Diff line number Diff line change
Expand Up @@ -724,3 +724,68 @@ void free(void *ptr)
__freelist_head->prev = cur;
__freelist_head = cur;
}

void snprintf(char *buffer, size_t n, char *str, ...)
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{
int *var_args = &str + 4;
int si = 0, bi = 0, pi = 0;

while (str[si]) {
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Could we reuse the code in sprintf() ?

if (bi >= n-1) {
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break;
} else if (str[si] != '%') {
buffer[bi] = str[si];
bi++;
si++;
} else {
int w = 0, zp = 0, pp = 0;

si++;
if (str[si] == '#') {
pp = 1;
si++;
}
if (str[si] == '0') {
zp = 1;
si++;
}
if (str[si] >= '1' && str[si] <= '9') {
w = str[si] - '0';
si++;
if (str[si] >= '0' && str[si] <= '9') {
w = w * 10;
w += str[si] - '0';
si++;
}
}
switch (str[si]) {
case 37: /* % */
buffer[bi++] = '%';
si++;
continue;
case 99: /* c */
buffer[bi++] = var_args[pi];
break;
case 115: /* s */
strcpy(buffer + bi, var_args[pi]);
bi += strlen(var_args[pi]);
break;
case 111: /* o */
bi += __format(buffer + bi, var_args[pi], w, zp, 8, pp);
break;
case 100: /* d */
bi += __format(buffer + bi, var_args[pi], w, zp, 10, 0);
break;
case 120: /* x */
bi += __format(buffer + bi, var_args[pi], w, zp, 16, pp);
break;
default:
abort();
break;
}
pi++;
si++;
}
}
if (bi < n) buffer[bi] = '\0';
}
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When using git for version control, it is recommended to add a newline at the end of files. This is because git compares files line by line, and the end of each line is identified by a newline character.

For more details, refer to the following link:
https://medium.com/@alexey.inkin/how-to-force-newline-at-end-of-files-and-why-you-should-do-it-fdf76d1d090e

19 changes: 19 additions & 0 deletions tests/driver.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -1085,4 +1085,23 @@ int main()
return 0;
}
EOF

try_output "Hello World 1123" << EOF
int main() {
char buffer[50];
snprintf(buffer, sizeof(buffer), "Hello %s %d", "World", 1123);
printf("%s", buffer);
return 0;
}
EOF

try_output "Number: -37" << EOF
int main() {
char buffer[20];
snprintf(buffer, sizeof(buffer), "Number: %d", -37);
printf("%s", buffer);
return 0;
}
EOF
Comment on lines +1089 to +1105
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I don't to see any edge case here, please add an edge case that covers when given formatted string's length exceeds n.


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Could you provide more tests such as string truncation?

echo OK
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