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_AWK AS A C CODE GENERATOR_ by Wahhab Baldwin

[LISTING ONE]

# This program reads a C structure and produces C code # to write the record to a C-ISAM work area. # There are limitations on the input format: see sample

BEGIN { FS = "[ \t[]+" # Override default

    }                                 #    field separators

$1 == "struct" && $3 == "{" { # Opening record struct

          rec = $2
          print "/*  " $2 "  */"
          offset = 0
     }

$2 == "struct" && $3 == "{" { # Struct within record

          type = "struct"
          j = 0
     }

$2 == "long" { f(type == "struct", "stlong", $3, 4)} $2 == "int" { f(type == "struct", "stint", $3, 2)} $2 == "float" { f(type == "struct", "stfloat", $3, 4)} $2 == "double" { f(type == "struct", "stdbl", $3, 8)} $2 == "char" && NF > 3 { # String

                  f(type == "struct", "stchar",  $3, $4 - 1)}

$2 == "char" && NF == 3 { # Single character

                  f(type == "struct", "stchar",  $3, 1)}

$2 == "}" && NF > 3 { # Array of structs

          type = ""
          print "\tfor (i = 0; i < " $4 + 0 "; i++) {"
          for (k = 0; k < j; k++) {
              gsub(";", "", name[k])
              temp = $3 "[i]." name[k]
              emit2("\t" stype[k], temp, flen[k])
          }
          print "\t}"
          offset += ($4 - 1) * slen
          slen = 0
      }

$2 == "}" && NF == 3 { # Named struct

          type = ""
          for (k = 0; k < j; k++)
              emit(stype[k], $3 "." name[k], flen[k])
          slen = 0
      }

function f(bool, str, x, y) {

         if (bool)
              setup(str, x, y)
          else
              emit(str, x, y)
      }

function setup(type, varname, l) { # Save field data in array

          name[j] = varname
          stype[j] = type
          flen[j++] = l
          slen += l
      }

function emit(type, varname, l) { # Print C code for field

          gsub(";", "", varname)
          print "\t" type "(p." rec "->" varname,
              ", inf_rec + " offset \
              (type == "ststring" ? ", " l ");" : ");")
          offset += l
      }

function emit2(type, varname, l) { # Print C code for field in struct

          gsub(";", "", varname)
          print "\t" type "(p." rec "->" varname,
              ", inf_rec + i * " slen, "+",
              offset (type ~ /string/ ? ", " l ");": ");")
          offset += l
      }

[Example 1: Simple AWK program to total a series of numbers]

{total += $1} END {print total} # Total for all input

[Example 2: Built-in AWK function for global substitution]

{gsub(/aluminium/, "aluminum")}
{gsub(/colour/, "color")}

[Example 3: Using strings rather than integers as array subscripts]

         # Program to count word usage in input.
         # eliminate all non-letters except space
         {    gsub(/[^A-Za-z ]/, "")        }

         # add words to associative array
         {    for (i = 1; i <= NF; i++)
                   ++word[$i] }

         # print each array entry
    END  {    for (j in word)
                   print j, word[j] }

[Example 4: Alternative to using the ? operator]

    if (type ~ /string/)
         last_part = ", " l ");"
    else
         last_part = ");"
    print "\t" type "(p." rec "->" varname
         ", inf_rec + " offset last_part