Hand-rolled itoa and test

Author: thalassemia

bson/_cbsonmodule.c

@@ -1036,7 +1036,7 @@ static int _write_element_to_buffer(PyObject* self, buffer_t buffer,
             if (list_type_byte == -1) {
                 return 0;
             }
-            int10_to_str((int)i, name);
+            itoa((long int)i, name);
             if (!buffer_write_bytes(buffer, name, (int)strlen(name) + 1)) {
                 return 0;
             }

bson/_cbsonmodule.h

@@ -30,27 +30,50 @@
 #endif
 
 /* Converts integer to its string representation in decimal notation. */
-static char *int10_to_str(long int val, char *dst)
-{
-    char buffer[65];
-    char *p;
-    long int new_val;
-    unsigned long int uval = (unsigned long int) val;
-
-    p = &buffer[sizeof(buffer)-1];
-    *p = '\0';
-    new_val= (long) (uval / 10);
-    *--p = '0'+ (char) (uval - (unsigned long) new_val * 10);
-    val = new_val;
-
-    while (val != 0)
-    {
-        new_val=val/10;
-        *--p = '0' + (char) (val-new_val*10);
-        val= new_val;
+static void itoa(long int num, char* str) {
+    int index = 0;
+    int sign = 1;
+    // Convert to unsigned to handle -LLONG_MIN overflow
+    unsigned long int absNum;
+
+    // Handle the case of 0
+    if (num == 0) {
+        str[index++] = '0';
+        str[index] = '\0';
+        return;
+    }
+
+    // Handle negative numbers
+    if (num < 0) {
+        sign = -1;
+        absNum = -num;
+    } else {
+        absNum = num;
+    }
+
+    // Convert the number to string
+    int digit;
+    while (absNum > 0) {
+        digit = absNum % 10;
+        str[index++] = digit + '0';  // Convert digit to character
+        absNum /= 10;
+    }
+
+    // Add minus sign if negative
+    if (sign == -1) {
+        str[index++] = '-';
+    }
+
+    str[index] = '\0';  // Null terminator
+
+    // Reverse the string
+    int start = 0;
+    int end = index - 1;
+    while (start < end) {
+        char temp = str[start];
+        str[start++] = str[end];
+        str[end--] = temp;
     }
-    while ((*dst++ = *p++) != 0) ;
-    return dst-1;
 }
 
 typedef struct type_registry_t {

bson/test_int2str.c

@@ -0,0 +1,144 @@
+#include <stdio.h>
+#include <time.h>
+#include <assert.h>
+#include <string.h>
+#include <limits.h>
+
+static void itoa(long int num, char* str) {
+    int index = 0;
+    int sign = 1;
+    // Convert to unsigned to handle -LLONG_MIN overflow
+    unsigned long int absNum;
+
+    // Handle the case of 0
+    if (num == 0) {
+        str[index++] = '0';
+        str[index] = '\0';
+        return;
+    }
+
+    // Handle negative numbers
+    if (num < 0) {
+        sign = -1;
+        absNum = -num;
+    } else {
+        absNum = num;
+    }
+
+    // Convert the number to string
+    int digit;
+    while (absNum > 0) {
+        digit = absNum % 10;
+        str[index++] = digit + '0';  // Convert digit to character
+        absNum /= 10;
+    }
+
+    // Add minus sign if negative
+    if (sign == -1) {
+        str[index++] = '-';
+    }
+
+    str[index] = '\0';  // Null terminator
+
+    // Reverse the string
+    int start = 0;
+    int end = index - 1;
+    while (start < end) {
+        char temp = str[start];
+        str[start++] = str[end];
+        str[end--] = temp;
+    }
+}
+
+static void int10_to_str(long int val, char *dst)
+{
+    char buffer[20];
+    char *p;
+    long int new_val;
+    unsigned long int uval = (unsigned long int) val;
+
+    if (val < 0)
+    {
+        *dst++ = '-';
+        /* Avoid integer overflow in (-val) for LLONG_MIN (BUG#31799). */
+        uval = (unsigned long int)0 - uval;
+    }
+
+    p = &buffer[sizeof(buffer)-1];
+    *p = '\0';
+    new_val= (long) (uval / 10);
+    *--p = '0'+ (char) (uval - (unsigned long) new_val * 10);
+    val = new_val;
+
+    while (val != 0)
+    {
+        new_val=val/10;
+        *--p = '0' + (char) (val-new_val*10);
+        val= new_val;
+    }
+    while ((*dst++ = *p++) != 0) ;
+    return;
+}
+
+static void INT2STRING(long int i, char* buffer) {
+    // Macro had access to allocated array but this function
+    // only has the pointer, so we hardcode buffer size
+    snprintf(buffer, 21, "%ld", i);
+    return;
+}
+
+void test(void (*f)(long int val, char* str), char* name) {
+    // Time common values
+    int reps = 10000;
+    float startTime, endTime;
+    startTime = (float)clock()/CLOCKS_PER_SEC;
+    for (int i = 0; i < reps; i++) {
+        for (long num = 0; num < 10000; num++) {
+            char str[20];
+            f(num, str);
+        }
+    }
+    endTime = (float)clock()/CLOCKS_PER_SEC;
+    printf("%s: %f\n", name, endTime - startTime);
+}
+
+int main() {
+    // Test extreme values
+    long int maxNum = (((size_t) - 1)>>1);
+    long int minNum = -maxNum-1;
+    char str_1[21];
+    char str_2[21];
+    char str_3[21];
+    itoa(maxNum, str_1);
+    int10_to_str(maxNum, str_2);
+    INT2STRING(maxNum, str_3);
+    assert(strcmp(str_1, str_2) == 0);
+    assert(strcmp(str_1, str_3) == 0);
+    memset(str_1,0,strlen(str_1));
+    memset(str_2,0,strlen(str_2));
+    memset(str_3,0,strlen(str_3));
+    itoa(minNum, str_1);
+    int10_to_str(minNum, str_2);
+    INT2STRING(minNum, str_3);
+    assert(strcmp(str_1, str_2) == 0);
+    assert(strcmp(str_1, str_3) == 0);
+
+    // Test common values
+    for (long num = 0; num < 10000; num++) {
+        char str_1[21];
+        char str_2[21];
+        char str_3[21];
+        itoa(num, str_1);
+        int10_to_str(num, str_2);
+        INT2STRING(num, str_3);
+        assert(strcmp(str_1, str_2) == 0);
+        assert(strcmp(str_1, str_3) == 0);
+    }
+
+    // Time common values
+    test(itoa, "itoa");
+    test(int10_to_str, "int10_to_str");
+    test(INT2STRING, "INT2STRING");
+
+    return 0;
+}

pymongo/_cmessagemodule.c

@@ -762,7 +762,7 @@ _batched_write_command(
         int cur_size;
         int enough_data = 0;
         char key[16];
-        int10_to_str(idx, key);
+        itoa(idx, key);
         if (!buffer_write_bytes(buffer, "\x03", 1) ||
             !buffer_write_bytes(buffer, key, (int)strlen(key) + 1)) {
             goto fail;