feat(esp_rom): Adds esp_rom_cvt func for logging and rom_vprintf

Author: KonstantinKondrashov

components/esp_rom/include/esp_rom_sys.h

@@ -53,6 +53,34 @@ int esp_rom_printf(const char *fmt, ...);
  */
 int esp_rom_vprintf(const char *fmt, va_list ap);
 
+/**
+ * @brief Convert an unsigned integer value to a string representation in the specified radix.
+ *
+ * This function converts the given unsigned integer value to a string representation in the specified radix.
+ * The resulting string is stored in the provided character buffer `buf`.
+ *
+ * @param[in] val    The unsigned integer value to be converted.
+ * @param[in] radix  The base of the numeral system to be used for the conversion.
+ *                   It determines the number of unique digits in the numeral system
+ *                   (e.g., 2 for binary, 10 for decimal, 16 for hexadecimal).
+ * @param[in] pad    The optional padding width (0 - unused) for the resulting string. It adds zero-padding.
+ *                   (val=123, pad=6 -> result=000123).
+ * @param[in] digits Pointer to a character array representing the digits of the
+ *                   numeral system. The array must contain characters in the order of increasing
+ *                   values, corresponding to the digits of the radix. For example, "0123456789ABCDEF"
+ *                   or hexadecimal.
+ * @param[out] buf   Pointer to the character buffer where the resulting string will
+ *                   be stored. The buffer must have enough space to accommodate the entire converted
+ *                   string, including the null-terminator.
+ *
+ * @return The length of the resulting string (excluding the null-terminator).
+ *
+ * @note The buffer `buf` must have sufficient space to hold the entire converted string, including the null-terminator.
+ *       The caller is responsible for ensuring the buffer's size is large enough to prevent buffer overflow.
+ * @note The provided `digits` array must have enough elements to cover the entire radix used for conversion. Otherwise, undefined behavior may occur.
+ */
+int esp_rom_cvt(unsigned long long val, long radix, int pad, const char *digits, char *buf);
+
 /**
  * @brief Pauses execution for us microseconds
  *

components/esp_rom/patches/esp_rom_print.c

@@ -14,34 +14,52 @@
 #include "rom/ets_sys.h"
 #include "sdkconfig.h"
 
-#if !ESP_ROM_HAS_VPRINTF_FUNC
-static int _cvt(unsigned long long val, char *buf, long radix, const char *digits)
+int esp_rom_cvt(unsigned long long val, long radix, int pad, const char *digits, char *buf)
 {
-#ifdef SUPPORT_LITTLE_RADIX
-    char temp[64];
-#else
-    char temp[32];
-#endif
-    char *cp = temp;
+    char *orig_buf = buf;
     int length = 0;
 
-    if (val == 0) {
-        /* Special case */
-        *cp++ = '0';
-    } else {
-        while (val) {
-            *cp++ = digits[val % radix];
-            val /= radix;
-        }
+    if (radix <= 0 || digits == NULL || buf == NULL) {
+        return 0;
     }
-    while (cp != temp) {
-        *buf++ = *--cp;
+
+    // The comments below show an example of the conversion process for val = 123 and pad = 6
+    do {
+        *buf++ = digits[val % radix];
+        val /= radix;
+        length++;
+    } while (val);
+    //        3   2   1
+    // buf = [0] [1] [2] [3]
+
+    // length = 3, pad = 6
+    while (pad > 0 && pad > length) {
+        *buf++ = '0';
         length++;
     }
     *buf = '\0';
+    // length = 6
+    //        3   2   1   0   0   0  \0
+    // buf = [0] [1] [2] [3] [4] [5] [6]
+
+    --buf;
+    // reverse the order of characters
+    //             3   2   1   0   0   0  \0
+    //            [0] [1] [2] [3] [4] [5] [6]
+    // orig_buf -- ^                   ^ ----- buf
+    while (orig_buf < buf) {
+        char first_char = *orig_buf;
+        char last_char = *buf;
+        *buf-- = first_char;
+        *orig_buf++ = last_char;
+    }
+    //        0   0   0   1   2   3  \0
+    // buf = [0] [1] [2] [3] [4] [5] [6]
+
     return (length);
 }
 
+#if !ESP_ROM_HAS_VPRINTF_FUNC
 #define is_digit(c) ((c >= '0') && (c <= '9'))
 static int ets_vprintf(void (*putc)(char c), const char *fmt, va_list ap)
 {
@@ -151,14 +169,14 @@ static int ets_vprintf(void (*putc)(char c), const char *fmt, va_list ap)
                 case 'D':
                 case 'u':
                 case 'U':
-                    length = _cvt(val, buf, 10, "0123456789");
+                    length = esp_rom_cvt(val, 10, 0, "0123456789", buf);
                     break;
                 case 'p':
                 case 'x':
-                    length = _cvt(val, buf, 16, "0123456789abcdef");
+                    length = esp_rom_cvt(val, 16, 0, "0123456789abcdef", buf);
                     break;
                 case 'X':
-                    length = _cvt(val, buf, 16, "0123456789ABCDEF");
+                    length = esp_rom_cvt(val, 16, 0, "0123456789ABCDEF", buf);
                     break;
                 }
                 cp = buf;

components/log/src/util.c

@@ -5,54 +5,19 @@
  */
 
 #include <stdint.h>
+#include "esp_rom_sys.h"
 
 int esp_log_util_cvt(unsigned long long val, long radix, int pad, const char *digits, char *buf)
 {
-    char *orig_buf = buf;
-    int length = 0;
-
-    // val = 123
-    do {
-        *buf++ = digits[val % radix];
-        val /= radix;
-        length++;
-    } while (val);
-    //        3   2   1
-    // buf = [0] [1] [2] [3]
-
-    // length = 3, pad = 6
-    while (pad > 0 && pad > length) {
-        *buf++ = '0';
-        length++;
-    }
-    *buf = '\0';
-    // length = 6
-    //        3   2   1   0   0   0  \0
-    // buf = [0] [1] [2] [3] [4] [5] [6]
-
-    --buf;
-    // reverse the order of characters
-    //             3   2   1   0   0   0  \0
-    //            [0] [1] [2] [3] [4] [5] [6]
-    // orig_buf -- ^                   ^ ----- buf
-    while (orig_buf < buf) {
-        char first_char = *orig_buf;
-        char last_char = *buf;
-        *buf-- = first_char;
-        *orig_buf++ = last_char;
-    }
-    //        0   0   0   1   2   3  \0
-    // buf = [0] [1] [2] [3] [4] [5] [6]
-
-    return (length);
+    return esp_rom_cvt(val, radix, pad, digits, buf);
 }
 
 int esp_log_util_cvt_hex(unsigned long long val, int pad, char *buf)
 {
-    return esp_log_util_cvt(val, 16, pad, "0123456789abcdef", buf);
+    return esp_rom_cvt(val, 16, pad, "0123456789abcdef", buf);
 }
 
 int esp_log_util_cvt_dec(unsigned long long val, int pad, char *buf)
 {
-    return esp_log_util_cvt(val, 10, pad, "0123456789", buf);
+    return esp_rom_cvt(val, 10, pad, "0123456789", buf);
 }