116 lines
3.6 KiB
Plaintext
116 lines
3.6 KiB
Plaintext
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_AWK AS A C CODE GENERATOR_
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by Wahhab Baldwin
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[LISTING ONE]
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# This program reads a C structure and produces C code
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# to write the record to a C-ISAM work area.
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# There are limitations on the input format: see sample
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BEGIN { FS = "[ \t[]+" # Override default
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} # field separators
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$1 == "struct" && $3 == "{" { # Opening record struct
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rec = $2
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print "/* " $2 " */"
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offset = 0
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}
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$2 == "struct" && $3 == "{" { # Struct within record
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type = "struct"
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j = 0
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}
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$2 == "long" { f(type == "struct", "stlong", $3, 4)}
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$2 == "int" { f(type == "struct", "stint", $3, 2)}
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$2 == "float" { f(type == "struct", "stfloat", $3, 4)}
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$2 == "double" { f(type == "struct", "stdbl", $3, 8)}
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$2 == "char" && NF > 3 { # String
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f(type == "struct", "stchar", $3, $4 - 1)}
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$2 == "char" && NF == 3 { # Single character
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f(type == "struct", "stchar", $3, 1)}
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$2 == "}" && NF > 3 { # Array of structs
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type = ""
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print "\tfor (i = 0; i < " $4 + 0 "; i++) {"
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for (k = 0; k < j; k++) {
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gsub(";", "", name[k])
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temp = $3 "[i]." name[k]
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emit2("\t" stype[k], temp, flen[k])
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}
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print "\t}"
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offset += ($4 - 1) * slen
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slen = 0
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}
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$2 == "}" && NF == 3 { # Named struct
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type = ""
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for (k = 0; k < j; k++)
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emit(stype[k], $3 "." name[k], flen[k])
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slen = 0
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}
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function f(bool, str, x, y) {
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if (bool)
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setup(str, x, y)
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else
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emit(str, x, y)
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}
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function setup(type, varname, l) { # Save field data in array
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name[j] = varname
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stype[j] = type
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flen[j++] = l
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slen += l
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}
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function emit(type, varname, l) { # Print C code for field
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gsub(";", "", varname)
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print "\t" type "(p." rec "->" varname,
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", inf_rec + " offset \
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(type == "ststring" ? ", " l ");" : ");")
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offset += l
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}
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function emit2(type, varname, l) { # Print C code for field in struct
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gsub(";", "", varname)
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print "\t" type "(p." rec "->" varname,
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", inf_rec + i * " slen, "+",
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offset (type ~ /string/ ? ", " l ");": ");")
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offset += l
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}
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[Example 1: Simple AWK program to total a series of numbers]
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{total += $1}
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END {print total} # Total for all input
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[Example 2: Built-in AWK function for global substitution]
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{gsub(/aluminium/, "aluminum")}
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{gsub(/colour/, "color")}
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[Example 3: Using strings rather than integers as array subscripts]
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# Program to count word usage in input.
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# eliminate all non-letters except space
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{ gsub(/[^A-Za-z ]/, "") }
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# add words to associative array
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{ for (i = 1; i <= NF; i++)
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++word[$i] }
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# print each array entry
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END { for (j in word)
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print j, word[j] }
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[Example 4: Alternative to using the ? operator]
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if (type ~ /string/)
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last_part = ", " l ");"
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else
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last_part = ");"
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print "\t" type "(p." rec "->" varname
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", inf_rec + " offset last_part
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