恕我直言，您应该使用原始缓冲区进行输入/输出。这比猜测编译器对每个系统上的字段或结构的排序方式要便携得多（也更安全）。
此外，这将允许您打包/解包数据，而无需担心字节顺序或内存对齐。
本示例代码中的宏提取自the facil.io framework header：
/** Reads an unaligned network ordered byte stream to a 16 bit number. */
#define fio_str2u16(c) \
((uint16_t)(((uint16_t)(((uint8_t *)(c))[0]) << 8) | \
(uint16_t)(((uint8_t *)(c))[1])))
/** Reads an unaligned network ordered byte stream to a 32 bit number. */
#define fio_str2u32(c) \
((uint32_t)(((uint32_t)(((uint8_t *)(c))[0]) << 24) | \
((uint32_t)(((uint8_t *)(c))[1]) << 16) | \
((uint32_t)(((uint8_t *)(c))[2]) << 8) | \
(uint32_t)(((uint8_t *)(c))[3])))
/** Writes a local 16 bit number to an unaligned buffer in network order. */
#define fio_u2str16(buffer, i) \
do { \
((uint8_t *)(buffer))[0] = ((uint16_t)(i) >> 8) & 0xFF; \
((uint8_t *)(buffer))[1] = ((uint16_t)(i)) & 0xFF; \
} while (0);
/** Writes a local 32 bit number to an unaligned buffer in network order. */
#define fio_u2str32(buffer, i) \
do { \
((uint8_t *)(buffer))[0] = ((uint32_t)(i) >> 24) & 0xFF; \
((uint8_t *)(buffer))[1] = ((uint32_t)(i) >> 16) & 0xFF; \
((uint8_t *)(buffer))[2] = ((uint32_t)(i) >> 8) & 0xFF; \
((uint8_t *)(buffer))[3] = ((uint32_t)(i)) & 0xFF; \
} while (0);
void req_file_read(req_file *d, unsigned char * buffer){
d->byte_count = fio_str2u32(buffer);
d->start_pos = fio_str2u32(buffer + 4);
d->name_len = fio_str2u16(buffer + 8);
}
void req_file_write(unsigned char * buffer, req_file *d){
fio_u2str32(buffer, d->byte_count);
fio_u2str32(buffer + 4, d->start_pos);
fio_u2str16(buffer + 8, d->name_len);
}
这使得在任何系统上处理未对齐的内存访问以及网络字节排序变得更加容易。基于二进制的数学使得它既便携又节省空间。
编辑（X 宏）
根据 Lightness Races in Orbit 提出的 cmets 和关注点，这里有一个带有 X 宏的头文件，可用于自动创建 X_read / X_write 内联函数。
序列化的缺点是在使用宏声明结构时应该提供原始缓冲区的字节偏移量。
在此示例中，相同的标头包含多次，但结果不同。此外，读/写函数不必内联，这只是一个示例。
这是标题：
/* note there's NO include guard in the header file */
#ifndef H__FACIL_IO_MACROS
#define H__FACIL_IO_MACROS
/** Reads an unaligned network ordered byte stream to a 16 bit number. */
#define fio_str2u16(c) \
((uint16_t)(((uint16_t)(((uint8_t *)(c))[0]) << 8) | \
(uint16_t)(((uint8_t *)(c))[1])))
/** Reads an unaligned network ordered byte stream to a 32 bit number. */
#define fio_str2u32(c) \
((uint32_t)(((uint32_t)(((uint8_t *)(c))[0]) << 24) | \
((uint32_t)(((uint8_t *)(c))[1]) << 16) | \
((uint32_t)(((uint8_t *)(c))[2]) << 8) | \
(uint32_t)(((uint8_t *)(c))[3])))
/** Writes a local 16 bit number to an unaligned buffer in network order. */
#define fio_u2str16(buffer, i) \
do { \
((uint8_t *)(buffer))[0] = ((uint16_t)(i) >> 8) & 0xFF; \
((uint8_t *)(buffer))[1] = ((uint16_t)(i)) & 0xFF; \
} while (0);
/** Writes a local 32 bit number to an unaligned buffer in network order. */
#define fio_u2str32(buffer, i) \
do { \
((uint8_t *)(buffer))[0] = ((uint32_t)(i) >> 24) & 0xFF; \
((uint8_t *)(buffer))[1] = ((uint32_t)(i) >> 16) & 0xFF; \
((uint8_t *)(buffer))[2] = ((uint32_t)(i) >> 8) & 0xFF; \
((uint8_t *)(buffer))[3] = ((uint32_t)(i)) & 0xFF; \
} while (0);
/* convert SERIAL_STRUCT_NAME to actual name */
#define SERIAL_STRUCT_MAKE(struct_name) SERIAL_STRUCT_MAKE2(struct_name)
#endif
#if SERIALIZE_TYPE /* create the type */
#undef SERIALIZE_TYPE
#undef SERIAL_STRUCT_FIELD
#define SERIAL_STRUCT_FIELD(name, bits, pos) uint##bits##_t name
#undef SERIAL_STRUCT_MAKE2
#define SERIAL_STRUCT_MAKE2(struct_name) \
typedef struct { \
SERIAL_STRUCT_FIELDS; \
} struct_name##_s;
/* perform macros */
SERIAL_STRUCT_MAKE(SERIAL_STRUCT_NAME)
#elif SERIALIZE_READ /* create reader function */
#undef SERIALIZE_READ
#undef SERIAL_STRUCT_FIELD
#define SERIAL_STRUCT_FIELD(name, bits, pos) \
dest->name = fio_str2u##bits((src + (pos)))
#undef SERIAL_STRUCT_MAKE2
#define SERIAL_STRUCT_MAKE2(struct_name) \
inline static void struct_name_read(struct_name##_s *dest, \
unsigned char *src) { \
SERIAL_STRUCT_FIELDS; \
}
/* perform macros */
SERIAL_STRUCT_MAKE(SERIAL_STRUCT_NAME)
#elif SERIALIZE_WRITE /* create writer function */
#undef SERIALIZE_WRITE
#undef SERIAL_STRUCT_FIELD
#define SERIAL_STRUCT_FIELD(name, bits, pos) \
fio_u2str##bits((dest + (pos)), src->name)
#undef SERIAL_STRUCT_MAKE2
#define SERIAL_STRUCT_MAKE2(struct_name) \
inline static void struct_name##_write(unsigned char *dest, \
struct_name##_s *src) { \
SERIAL_STRUCT_FIELDS; \
}
/* perform macros */
SERIAL_STRUCT_MAKE(SERIAL_STRUCT_NAME)
#endif
在实现文件中，信息可能如下所示（同样，内联方法可以更改）：
/* will produce req_file_s as the struct name, but you can change that */
#define SERIAL_STRUCT_NAME req_file
#define SERIAL_STRUCT_FIELDS \
SERIAL_STRUCT_FIELD(start_pos, 32, 0); \
SERIAL_STRUCT_FIELD(byte_count, 32, 4); \
SERIAL_STRUCT_FIELD(name_len, 16, 8)
#define SERIALIZE_TYPE 1
#include "serialize.h"
#define SERIALIZE_READ 1
#include "serialize.h"
#define SERIALIZE_WRITE 1
#include "serialize.h"
这可以调整，所以SERIALIZE_TYPE 也声明了函数（没有定义它们），并且函数没有被内联（所以只有实现文件包含每种类型的头 3 次。