printf相关函数

 

int sprintf( char *buffer, const char *format, [ argument] … );

sprintf 返回以format为格式argument为内容组成的结果被写入buffer 的字节数，结束字符‘\0’不计入内。即，如果“Hello”被写入空间足够大的buffer后，函数sprintf 返回5。

 

int snprintf(char *str, size_t size, const char *format, ...); 

将可变个参数(...)按照format格式化成字符串，然后将其复制到str中； 

(1) 如果格式化后的字符串长度 < size，则将此字符串全部复制到str中，并给其后添加一个字符串结束符('\0')；若成功则返回欲写入的字符串长度，若出错则返回负值。

 

(2) 如果格式化后的字符串长度 >= size，则只将其中的(size-1)个字符复制到str中，并给其后添加一个字符串结束符('\0')，返回值为欲写入的字符串长度。

/**
 * Format a string and place it in a buffer
 *
 * @param buf	The buffer to place the result into
 * @param fmt	The format string to use
 * @param ...	Arguments for the format string
 *
 * The function returns the number of characters written
 * into @buf.
 *
 * See the vsprintf() documentation for format string extensions over C99.
 */
int sprintf(char *buf, const char *fmt, ...)
		__attribute__ ((format (__printf__, 2, 3)));
/**
 * Format a string and place it in a buffer (va_list version)
 *
 * @param buf	The buffer to place the result into
 * @param size	The size of the buffer, including the trailing null space
 * @param fmt	The format string to use
 * @param args	Arguments for the format string
 * @return the number of characters which have been written into
 * the @buf not including the trailing '\0'. If @size is == 0 the function
 * returns 0.
 *
 * If you're not already dealing with a va_list consider using scnprintf().
 *
 * See the vsprintf() documentation for format string extensions over C99.
 */
int vsprintf(char *buf, const char *fmt, va_list args);
char *simple_itoa(ulong i);


#ifdef CONFIG_SYS_VSNPRINTF
/**
 * Format a string and place it in a buffer
 *
 * @param buf	The buffer to place the result into
 * @param size	The size of the buffer, including the trailing null space
 * @param fmt	The format string to use
 * @param ...	Arguments for the format string
 * @return the number of characters which would be
 * generated for the given input, excluding the trailing null,
 * as per ISO C99.  If the return is greater than or equal to
 * @size, the resulting string is truncated.
 *
 * See the vsprintf() documentation for format string extensions over C99.
 */
int snprintf(char *buf, size_t size, const char *fmt, ...)
		__attribute__ ((format (__printf__, 3, 4)));
/**
 * Format a string and place it in a buffer
 *
 * @param buf	The buffer to place the result into
 * @param size	The size of the buffer, including the trailing null space
 * @param fmt	The format string to use
 * @param ...	Arguments for the format string
 *
 * The return value is the number of characters written into @buf not including
 * the trailing '\0'. If @size is == 0 the function returns 0.
 *
 * See the vsprintf() documentation for format string extensions over C99.
 */
int scnprintf(char *buf, size_t size, const char *fmt, ...)
		__attribute__ ((format (__printf__, 3, 4)));
/**
 * Format a string and place it in a buffer (base function)
 *
 * @param buf	The buffer to place the result into
 * @param size	The size of the buffer, including the trailing null space
 * @param fmt	The format string to use
 * @param args	Arguments for the format string
 * @return The number characters which would be generated for the given
 * input, excluding the trailing '\0', as per ISO C99. Note that fewer
 * characters may be written if this number of characters is >= size.
 *
 * This function follows C99 vsnprintf, but has some extensions:
 * %pS output the name of a text symbol
 * %pF output the name of a function pointer
 * %pR output the address range in a struct resource
 *
 * The function returns the number of characters which would be
 * generated for the given input, excluding the trailing '\0',
 * as per ISO C99.
 *
 * Call this function if you are already dealing with a va_list.
 * You probably want snprintf() instead.
 */
int vsnprintf(char *buf, size_t size, const char *fmt, va_list args);

/**
 * Format a string and place it in a buffer (va_list version)
 *
 * @param buf	The buffer to place the result into
 * @param size	The size of the buffer, including the trailing null space
 * @param fmt	The format string to use
 * @param args	Arguments for the format string
 * @return the number of characters which have been written into
 * the @buf not including the trailing '\0'. If @size is == 0 the function
 * returns 0.
 *
 * If you're not already dealing with a va_list consider using scnprintf().
 *
 * See the vsprintf() documentation for format string extensions over C99.
 */
int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
#else
/*
 * Use macros to silently drop the size parameter. Note that the 'cn'
 * versions are the same as the 'n' versions since the functions assume
 * there is always enough buffer space when !CONFIG_SYS_VSNPRINTF
 */
#define snprintf(buf, size, fmt, args...) sprintf(buf, fmt, ##args)
#define scnprintf(buf, size, fmt, args...) sprintf(buf, fmt, ##args)
#define vsnprintf(buf, size, fmt, args...) vsprintf(buf, fmt, ##args)
#define vscnprintf(buf, size, fmt, args...) vsprintf(buf, fmt, ##args)
#endif /* CONFIG_SYS_VSNPRINTF */

/**
 * print_grouped_ull() - print a value with digits grouped by ','
 *
 * This prints a value with grouped digits, like 12,345,678 to make it easier
 * to read.
 *
 * @val:	Value to print
 * @digits:	Number of digiits to print
 */
void print_grouped_ull(unsigned long long int_val, int digits);

#endif