Add func kernaux_utoa10

include/kernaux/itoa.h

@@ -5,8 +5,16 @@
 extern "C" {
 #endif
 
+#include <stdint.h>
+
+// uint64_t: "18446744073709551615"
+#define KERNAUX_ITOA_BUFFER_SIZE 21
+
+// TODO: remove this
 void kernaux_itoa(int d, char *buf, int base);
 
+void kernaux_utoa10(uint64_t value, char *buffer);
+
 #ifdef __cplusplus
 }
 #endif

src/itoa.c

@@ -3,6 +3,7 @@
 #endif
 
 #include <kernaux/itoa.h>
+#include <kernaux/libc.h>
 
 void kernaux_itoa(const int d, char *buf, const int base)
 {
@@ -43,3 +44,23 @@ void kernaux_itoa(const int d, char *buf, const int base)
         p2--;
     }
 }
+
+void kernaux_utoa10(uint64_t value, char *buffer)
+{
+    char *pos = buffer;
+
+    if (value == 0) *(pos++) = '0';
+
+    while (value > 0) {
+        *(pos++) = value % 10 + '0';
+        value = value / 10;
+    }
+
+    *(pos--) = '\0';
+
+    while (buffer < pos) {
+        const char tmp = *buffer;
+        *(buffer++) = *pos;
+        *(pos--)    = tmp;
+    }
+}

tests/test_itoa.c

@@ -7,6 +7,45 @@
 #include <assert.h>
 #include <string.h>
 
+static const struct {
+    uint64_t value;
+    const char *result;
+} utoa10_cases[] = {
+    { 0,                        "0" },
+    { 1,                        "1" },
+    { 2,                        "2" },
+    { 9,                        "9" },
+    { 10,                       "10" },
+    { 11,                       "11" },
+    { 12,                       "12" },
+    { 19,                       "19" },
+    { 20,                       "20" },
+    { 21,                       "21" },
+    { 99,                       "99" },
+    { 100,                      "100" },
+    { 101,                      "101" },
+    { 199,                      "199" },
+    { 200,                      "200" },
+    { 201,                      "201" },
+    { 999,                      "999" },
+    { 1000,                     "1000" },
+    { 1001,                     "1001" },
+    { 1999,                     "1999" },
+    { 2000,                     "2000" },
+    { 2001,                     "2001" },
+    { 9999,                     "9999" },
+    { 10000,                    "10000" },
+    { 10001,                    "10001" },
+    { UINT16_MAX,               "65535" },
+    { UINT16_MAX + 1,           "65536" },
+    { UINT32_MAX,               "4294967295" },
+    { (uint64_t)UINT32_MAX + 1, "4294967296" },
+    { UINT64_MAX - 6,           "18446744073709551609" },
+    { UINT64_MAX - 5,           "18446744073709551610" },
+    { UINT64_MAX - 1,           "18446744073709551614" },
+    { UINT64_MAX,               "18446744073709551615" },
+};
+
 int main()
 {
     {
@@ -33,5 +72,16 @@ int main()
         assert(buffer[5] == '\0');
     }
 
+    char buffer[KERNAUX_ITOA_BUFFER_SIZE];
+
+    for (
+        size_t index = 0;
+        index < sizeof(utoa10_cases) / sizeof(utoa10_cases[0]);
+        ++index
+    ) {
+        kernaux_utoa10(utoa10_cases[index].value, buffer);
+        assert(strcmp(buffer, utoa10_cases[index].result) == 0);
+    }
+
     return 0;
 }