btstack_util: add safe versions of snprintf

src/btstack_util.c

@@ -45,16 +45,14 @@
 #include "btstack_debug.h"
 #include "btstack_util.h"
 
+#include <stdio.h>  // vsnprintf
+#include <string.h> // memcpy
+
 #ifdef _MSC_VER
 #include <intrin.h>
 #include <windows.h>
 #endif
 
-#ifdef ENABLE_PRINTF_HEXDUMP
-#include <stdio.h>
-#endif
-
-#include <string.h>
 
 /**
  * @brief Compare two Bluetooth addresses
@@ -641,6 +639,42 @@ void btstack_strcat(char * dst, uint16_t dst_size, const char * src){
     dst[dst_len + bytes_to_copy] = 0;
 }
 
+int btstack_printf_strlen(const char * format, ...){
+    va_list argptr;
+    va_start(argptr, format);
+    char dummy_buffer[1];
+    int len = vsnprintf(dummy_buffer, sizeof(dummy_buffer), format, argptr);
+    va_end(argptr);
+    return len;
+}
+
+uint16_t btstack_snprintf_assert_complete(char * buffer, size_t size, const char * format, ...){
+    va_list argptr;
+    va_start(argptr, format);
+    int len = vsnprintf(buffer, size, format, argptr);
+    va_end(argptr);
+
+    // check for no error and no truncation
+    btstack_assert(len >= 0);
+    btstack_assert(len < size);
+    return (uint16_t) len;
+}
+
+uint16_t btstack_snprintf_best_effort(char * buffer, size_t size, const char * format, ...){
+    btstack_assert(size > 0);
+    va_list argptr;
+    va_start(argptr, format);
+    int len = vsnprintf(buffer, size, format, argptr);
+    va_end(argptr);
+    if (len < 0) {
+        // error -> len = 0
+        return 0;
+    } else {
+        // min of total string len and buffer size
+        return (uint16_t) btstack_min((uint32_t) len, (uint32_t) size - 1);
+    }
+}
+
 uint16_t btstack_virtual_memcpy(
     const uint8_t * field_data, uint16_t field_len, uint16_t field_offset, // position of field in complete data block
     uint8_t * buffer, uint16_t buffer_size, uint16_t buffer_offset){

src/btstack_util.h

@@ -377,6 +377,50 @@ uint16_t btstack_strcpy(char * dst, uint16_t dst_size, const char * src);
  */
 void btstack_strcat(char * dst, uint16_t dst_size, const char * src);
 
+/**
+ * @brief Calculated the number of characters that would get printed
+ * @note same as calling snprintf without a buffer
+ * @param format
+ * @param argsq
+ * @return number of characters, or negative value on error
+ */
+int btstack_printf_strlen(const char * format, ...)
+#ifdef __GNUC__
+__attribute__ ((format (__printf__, 1, 2)))
+#endif
+;
+
+
+/**
+ * @brief Format string into buffer with '\0' and assert it is large enough
+ * @note same as calling snprintf and assert that the string was not truncated
+ * @param buffer
+ * @param size of buffer
+ * @param format
+ * @param argsq
+ * @return number of characters
+ */
+uint16_t btstack_snprintf_assert_complete(char * buffer, size_t size, const char * format, ...)
+#ifdef __GNUC__
+__attribute__ ((format (__printf__, 3, 4)))
+#endif
+;
+
+/**
+ * @brief Format string into buffer, truncated if necessary. Output string is '\0' terminated
+ * @note similar to calling snprintf but returns the length of the output string
+ * @param buffer
+ * @param size of buffer
+ * @param format
+ * @param argsq
+ * @return number of characters
+ */
+uint16_t btstack_snprintf_best_effort(char * buffer, size_t size, const char * format, ...)
+#ifdef __GNUC__
+__attribute__ ((format (__printf__, 3, 4)))
+#endif
+;
+
 /**
  * Returns the number of leading 0-bits in x, starting at the most significant bit position.
  * If x is 0, the result is undefined.