[Embedded] convert binary data to c array

將二進位資料轉換成 C 語言的陣列，是程序員常會用到的一個小技巧。本篇以一個例子說明如何在 linux 環境下達到此目的。

假設目的是取出一個 wav file 的前 1024 bytes 的資料，將其轉換成 C Array，指令如下：

$ wget http://wav-sounds.com/wp-content/uploads/2017/09/Answer-02.wav 

$ dd skip=70 iflag=skip_bytes if=Answer-02.wav bs=1K count=1 of=./1024bytes.bin 

$ xxd -i 1024bytes.bin > test.h

dd 的參數說明：

skip=70 iflag=skip_bytes： 

略過 70 bytes。標準的 WAVE Header 應該是44bytes，但是此檔案多加了一些header，共有70bytes。

bs=1K count=1 :  

取出 1k 的資料，並且只做一次取出的動作

轉換後的資料如下：

unsigned char __1024bytes_bin[] = {
  0xff, 0xf3, 0x38, 0xc4, 0x00, 0x00, 0x00, 0x02, 0x5b, 0x20, 0x00, 0x00,
  0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xf3, 0x28, 0xc4, 0x5f, 0x00, 0x00, 0x02, 0x5b, 0x20, 0x00, 0x00,
  0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xf3, 0x38, 0xc4, 0x9a, 0x00, 0x00, 0x02, 0x5b, 0x20, 0x00, 0x00,
  0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xa7, 0x5e, 0x58, 0x24, 0x03, 0x42,
  0xc1, 0x5c, 0x00, 0x00, 0x21, 0x61, 0xb3, 0x33, 0x33, 0xfb, 0x12, 0x01,
  0xb8, 0x8e, 0xfb, 0x0b, 0x1c, 0xd6, 0xef, 0x08, 0x43, 0x3c, 0xe7, 0x39,
  0xb1, 0x96, 0xbc, 0xf6, 0x0a, 0x20, 0x15, 0xb7, 0x48, 0x10, 0x64, 0xd1,
  0xff, 0xf3, 0x28, 0xc4, 0xf9, 0x0d, 0x40, 0x02, 0x5b, 0x20, 0x00, 0x00,
  0x00, 0xcf, 0xcd, 0x74, 0x73, 0xd8, 0x42, 0x64, 0x8c, 0x5a, 0x3d, 0x20,
  0x0a, 0x12, 0x44, 0x28, 0x08, 0x0a, 0x18, 0x5c, 0x56, 0x09, 0x93, 0x94,
  0x00, 0x60, 0x6c, 0x9e, 0xa1, 0x97, 0x39, 0xc3, 0x27, 0x3a, 0x40, 0x28,
  0x24, 0x5c, 0x10, 0x0c, 0x31, 0x68, 0xd1, 0xa3, 0x91, 0x00, 0x26, 0x1b,
  0x6e, 0x0c, 0x65, 0xce, 0x70, 0xcb, 0x9e, 0xc1, 0x03, 0x0b, 0x8a, 0x09,
  0xff, 0xf3, 0x38, 0xc4, 0xff, 0x17, 0xc0, 0x02, 0x5b, 0x20, 0x00, 0x00,
  0x00, 0x18, 0xb9, 0xcf, 0xd2, 0x02, 0x76, 0xea, 0x10, 0x9a, 0x34, 0x74,
  0x8d, 0x1b, 0x7b, 0x05, 0x10, 0x62, 0xe2, 0x82, 0x4c, 0x9c, 0xf6, 0xa1,
  0x09, 0xed, 0x43, 0x2e, 0x73, 0x82, 0x34, 0x73, 0xa8, 0x43, 0x2d, 0x72,
  0x46, 0x05, 0xf8, 0x00, 0x08, 0x30, 0xab, 0xee, 0x4a, 0x28, 0x52, 0x00,
  0xc3, 0x68, 0x02, 0x0c, 0x12, 0x62, 0xa4, 0x1c, 0x20, 0x79, 0xf4, 0xca,
  0x81, 0x03, 0x23, 0x30, 0x20, 0x98, 0x15, 0x27, 0x1b, 0x92, 0xd4, 0x59,
  0xce, 0x0a, 0x08, 0x1a, 0x04, 0x80, 0xba, 0x39, 0xd6, 0x39, 0x49, 0x9d,
  0x30, 0x4e, 0xc6, 0xf4, 0xc4, 0xac, 0xa2, 0x22, 0xc6, 0x10, 0x4c, 0x92,
  0xff, 0xf3, 0x28, 0xc4, 0xff, 0x0e, 0xc0, 0x02, 0x5b, 0x20, 0x00, 0x00,
  0x00, 0x62, 0xe3, 0x47, 0x62, 0x8b, 0xc3, 0x24, 0x9a, 0x4f, 0x2e, 0x0c,
  0xa2, 0x29, 0x2e, 0xb4, 0xdd, 0x04, 0x25, 0x83, 0xdc, 0xa6, 0x43, 0x24,
  0x0d, 0x0e, 0xa0, 0x7c, 0xc8, 0xb8, 0x77, 0xf8, 0x98, 0x17, 0x47, 0x99,
  0x26, 0xe9, 0x8c, 0x39, 0x22, 0x5f, 0x1d, 0x83, 0xb0, 0x7f, 0x25, 0x90,
  0xff, 0x99, 0x16, 0x16, 0x27, 0x4c, 0xc8, 0xa0, 0x91, 0x1c, 0x80, 0x5f,
  0xff, 0xf3, 0x38, 0xc4, 0xff, 0x22, 0xaa, 0xd9, 0x88, 0x01, 0x4c, 0x48,
  0x01, 0x25, 0x0c, 0x1c, 0xd9, 0x11, 0xef, 0xff, 0xf5, 0x3b, 0xa0, 0xc9,
  0xbb, 0xf3, 0x7b, 0x1c, 0x34, 0x73, 0x45, 0x29, 0x22, 0xe3, 0xff, 0xff,
  0x4d, 0xd3, 0x41, 0x68, 0x1a, 0x2c, 0xff, 0x10, 0x14, 0x40, 0x39, 0x00,
  0x0d, 0x18, 0xc2, 0x08, 0x1c, 0x8a, 0x04, 0x20, 0x84, 0x42, 0x00, 0x06,
  0x84, 0x47, 0x64, 0xe4, 0xc4, 0xd2, 0xe8, 0xd3, 0xd7, 0x0c, 0x28, 0x06,
  0xed, 0x24, 0xb5, 0xdb, 0x58, 0xc1, 0xc2, 0x78, 0x5a, 0xb5, 0xa8, 0x61,
  0x9a, 0x3c, 0xde, 0x6e, 0x92, 0x02, 0x41, 0x0c, 0x41, 0x90, 0x43, 0xe8,
  0x39, 0x34, 0x30, 0x01, 0xc0, 0x26, 0x07, 0xb0, 0x81, 0x1c, 0x8a, 0x58,
  0xff, 0xf3, 0x28, 0xc4, 0xd3, 0x25, 0x82, 0xd2, 0x61, 0x95, 0x9a, 0x69,
  0x22, 0xb9, 0x28, 0x9c, 0x68, 0xe1, 0xd6, 0x4f, 0xea, 0x5a, 0x47, 0x55,
  0xcf, 0xbd, 0xb2, 0xf6, 0x4d, 0xe6, 0xe4, 0xfb, 0xe2, 0x0c, 0x53, 0x51,
  0xcc, 0xd9, 0xde, 0x5c, 0x74, 0x75, 0x82, 0x61, 0xa1, 0x31, 0xe5, 0xc2,
  0xf1, 0xc1, 0x2d, 0x87, 0x9b, 0x50, 0xf6, 0x56, 0xd9, 0xb3, 0x78, 0x37,
  0xbf, 0x86, 0x63, 0xd9, 0x71, 0x6f, 0xf3, 0xc3, 0x2b, 0xe1, 0xf1, 0xfd,
  0xff, 0xf3, 0x38, 0xc4, 0x78, 0x25, 0x32, 0xfa, 0x7d, 0xd7, 0x9b, 0x58,
  0x01, 0x3b, 0xd8, 0xce, 0xe9, 0x90, 0xce, 0xdc, 0xf3, 0x56, 0xd4, 0xf1,
  0x51, 0x0c, 0xae, 0x22, 0xdf, 0xf3, 0x7f, 0xfd, 0xec, 0x63, 0x36, 0x71,
  0xff, 0xed, 0x6d, 0x9f, 0xcc, 0x10, 0x20, 0x25, 0x00, 0x00, 0x0b, 0x53,
  0xa8, 0xc2, 0x50, 0x34, 0xb8, 0x80, 0x03, 0xec, 0x59, 0x4c, 0x86, 0x26,
  0xd0, 0xb7, 0x30, 0x9c, 0x93, 0x8f, 0x42, 0xf4, 0x80, 0x9f, 0x88, 0x43,
  0xab, 0x19, 0x5f, 0x8f, 0xbe, 0x12, 0x8f, 0xcf, 0x52, 0xe7, 0x72, 0xfe,
  0x4c, 0x5b, 0x11, 0xad, 0xdb, 0xec, 0x73, 0x5f, 0xb1, 0x2b, 0x20, 0x69,
  0xff, 0xa6, 0x77, 0x1f, 0x1e, 0xfe, 0xf4, 0xdf, 0xf9, 0xa5, 0xeb, 0x37,
  0xff, 0xf3, 0x28, 0xc4, 0x42, 0x1a, 0x01, 0x1e, 0xcd, 0xbf, 0x98, 0x79,
  0x00, 0xc7, 0xbe, 0xbd, 0xbe, 0xb5, 0xa8, 0x66, 0x45, 0xeb, 0x70, 0xd7,
  0x90, 0x21, 0x22, 0x9d, 0xac, 0xe5, 0xd9, 0x8c, 0x04, 0x19, 0xe5, 0x86,
  0x3f, 0x9a, 0x0b, 0x7d, 0x23, 0x43, 0x66, 0x1f, 0xbc, 0xe0, 0x3a, 0x8f,
  0x50, 0x45, 0x3f, 0x88, 0x0b, 0x51, 0x26, 0xe0, 0x0e, 0xb5, 0xff, 0xf6,
  0x08, 0x91, 0x0a, 0xd1, 0xed, 0x34, 0x75, 0x81, 0x5a, 0x8d, 0xe9, 0x11,
  0xff, 0xf3, 0x38, 0xc4, 0x15, 0x10, 0xc1, 0x72, 0xe5, 0x5f, 0xc9, 0x28,
  0x00, 0x31, 0x0c, 0x15, 0x83, 0x21, 0x43, 0x04, 0x67, 0x10, 0x6b, 0x23,
  0x7f, 0xe4, 0xa2, 0x48, 0xe8, 0x53, 0xf3, 0x89, 0xb5, 0x64, 0x2c, 0xac,
  0xa7, 0x31, 0x08, 0xcd, 0xe4, 0xfd, 0x46, 0x1c, 0x63, 0xff, 0xa9, 0xeb,
  0x26, 0x43, 0xff, 0xff, 0xa4, 0x38, 0x0f, 0xb2, 0x04, 0x8a, 0x7f, 0x64,
  0x00, 0x0a, 0x00, 0x2e, 0x80, 0xa3, 0xfa, 0xfe, 0x45, 0x5e, 0x80, 0x48,
  0x44, 0x66, 0x5d, 0x64, 0x54, 0xfa, 0xd3, 0x96, 0xec, 0xe2, 0x8e, 0x16,
  0x6d, 0x41, 0x3e, 0xaf, 0xf7, 0xfd, 0x3f, 0xad, 0x66, 0xe2, 0x01, 0x61,
  0x18, 0x91, 0x0b, 0xf8, 0xda, 0xf2, 0xb9, 0xff, 0xc0, 0x20, 0x16, 0x37,
  0xff, 0xf3, 0x28, 0xc4, 0x31, 0x17, 0x01, 0x8a, 0xe5, 0x96, 0x43, 0x0d,
  0x0c, 0x73, 0x69, 0xf5
};
unsigned int __1024bytes_bin_len = 1024;

參考資料：

• https://linux.die.net/man/1/dd
• https://linux.die.net/man/1/xxd
• http://wav-sounds.com/