gperf
1.1、gperf简介
是什么 ?:a command-line tool that generates a perfect hash function from a given list of strings.
开发语言:C / C++
开发组织:GNU
官方主页:http://www.gnu.org/software/gperf
1.2、通过包管理器安装gperf
操作系统包管理器安装命令
WindowsChocolateychoco install -y gperf
macOSHomeBrewbrew install gperf
GNU/LinuxLinuxBrewbrew install gperf
aptsudo apt-get install -y gperf
CentOSyumsudo yum install -y gperf
dnfsudo dnf install -y gperf
openSUSEzyppersudo zypper install -y gperf
Alpine Linuxapksudo apk add gperf

Arch Linux

ArcoLinux

Manjaro Linux

pacmansudo pacman -Syyu --noconfirm
sudo pacman -S    --noconfirm gperf
Gentoo LinuxPortagesudo emerge gperf
1.3、通过编译源码安装gperf
1.4、gperf命令

示例:

echo "a\nb\nc" | gperf > xx.c

得到的xx.c代码如下:

/* C code produced by gperf version 3.0.3 */
/* Command-line: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/gperf  */
/* Computed positions: -k'1' */

#if !((' ' == 32) && ('!' == 33) && ('"' == 34) && ('#' == 35) \
      && ('%' == 37) && ('&' == 38) && ('\'' == 39) && ('(' == 40) \
      && (')' == 41) && ('*' == 42) && ('+' == 43) && (',' == 44) \
      && ('-' == 45) && ('.' == 46) && ('/' == 47) && ('0' == 48) \
      && ('1' == 49) && ('2' == 50) && ('3' == 51) && ('4' == 52) \
      && ('5' == 53) && ('6' == 54) && ('7' == 55) && ('8' == 56) \
      && ('9' == 57) && (':' == 58) && (';' == 59) && ('<' == 60) \
      && ('=' == 61) && ('>' == 62) && ('?' == 63) && ('A' == 65) \
      && ('B' == 66) && ('C' == 67) && ('D' == 68) && ('E' == 69) \
      && ('F' == 70) && ('G' == 71) && ('H' == 72) && ('I' == 73) \
      && ('J' == 74) && ('K' == 75) && ('L' == 76) && ('M' == 77) \
      && ('N' == 78) && ('O' == 79) && ('P' == 80) && ('Q' == 81) \
      && ('R' == 82) && ('S' == 83) && ('T' == 84) && ('U' == 85) \
      && ('V' == 86) && ('W' == 87) && ('X' == 88) && ('Y' == 89) \
      && ('Z' == 90) && ('[' == 91) && ('\\' == 92) && (']' == 93) \
      && ('^' == 94) && ('_' == 95) && ('a' == 97) && ('b' == 98) \
      && ('c' == 99) && ('d' == 100) && ('e' == 101) && ('f' == 102) \
      && ('g' == 103) && ('h' == 104) && ('i' == 105) && ('j' == 106) \
      && ('k' == 107) && ('l' == 108) && ('m' == 109) && ('n' == 110) \
      && ('o' == 111) && ('p' == 112) && ('q' == 113) && ('r' == 114) \
      && ('s' == 115) && ('t' == 116) && ('u' == 117) && ('v' == 118) \
      && ('w' == 119) && ('x' == 120) && ('y' == 121) && ('z' == 122) \
      && ('{' == 123) && ('|' == 124) && ('}' == 125) && ('~' == 126))
/* The character set is not based on ISO-646.  */
error "gperf generated tables don't work with this execution character set. Please report a bug to ."
#endif


#define TOTAL_KEYWORDS 4
#define MIN_WORD_LENGTH 1
#define MAX_WORD_LENGTH 1
#define MIN_HASH_VALUE 1
#define MAX_HASH_VALUE 8
/* maximum key range = 8, duplicates = 0 */

#ifdef __GNUC__
__inline
#else
#ifdef __cplusplus
inline
#endif
#endif
static unsigned int
hash (str, len)
     register const char *str;
     register unsigned int len;
{
  static unsigned char asso_values[] =
    {
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 7, 2, 5,
      0, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
      9, 9, 9, 9, 9, 9
    };
  return len + asso_values[(unsigned char)str[0]];
}

const char *
in_word_set (str, len)
     register const char *str;
     register unsigned int len;
{
  static const char * wordlist[] =
    {
      "",
      "d",
      "",
      "b",
      "", "",
      "c",
      "",
      "a"
    };

  if (len <= MAX_WORD_LENGTH && len >= MIN_WORD_LENGTH)
    {
      unsigned int key = hash (str, len);

      if (key <= MAX_HASH_VALUE)
        {
          register const char *s = wordlist[key];

          if (*str == *s && !strcmp (str + 1, s + 1))
            return s;
        }
    }
  return 0;
}