Work on graph build and metarule matching.

expand.go

@@ -0,0 +1,214 @@
+
+// String substitution and expansion.
+
+package main
+
+import (
+    "strings"
+    "unicode/utf8"
+)
+
+
+// Expand a word. This includes substituting variables and handling quotes.
+func expand(input string, vars map[string][]string, expandBackticks bool) string {
+	expanded := make([]byte, 0)
+	var i, j int
+	for i = 0; i < len(input); {
+		j = i + strings.IndexAny(input[i:], "\"'`$\\")
+
+		if j < 0 {
+			expanded = append(expanded, input[i:]...)
+			break
+		}
+
+		expanded = append(expanded, input[i:j]...)
+		c, w := utf8.DecodeRuneInString(input[j:])
+		i = j + w
+
+		var off int
+		var out string
+		switch c {
+		case '\\':
+			out, off = expandEscape(input[i:])
+
+		case '"':
+			out, off = expandDoubleQuoted(input[i:], vars, expandBackticks)
+
+		case '\'':
+			out, off = expandSingleQuoted(input[i:])
+
+		case '`':
+            if expandBackticks {
+                out, off = expandBackQuoted(input[i:], vars)
+            } else {
+                out = input
+                off = len(input)
+            }
+
+		case '$':
+            out, off = expandSigil(input[i:], vars)
+		}
+
+		expanded = append(expanded, out...)
+		i += off
+	}
+
+	return string(expanded)
+}
+
+// Expand following a '\\'
+func expandEscape(input string) (string, int) {
+	c, w := utf8.DecodeRuneInString(input)
+	return string(c), w
+}
+
+// Expand a double quoted string starting after a '\"'
+func expandDoubleQuoted(input string, vars map[string][]string, expandBackticks bool) (string, int) {
+	// find the first non-escaped "
+	j := 0
+	for {
+		j = strings.IndexAny(input[j:], "\"\\")
+		if j < 0 {
+			break
+		}
+
+		_, w := utf8.DecodeRuneInString(input[j:])
+		j += w
+
+		c, w := utf8.DecodeRuneInString(input[j:])
+		j += w
+
+		if c == '"' {
+			return expand(input[:j], vars, expandBackticks), (j + w)
+		}
+
+		if c == '\\' {
+			if j+w < len(input) {
+				j += w
+				_, w := utf8.DecodeRuneInString(input[j:])
+				j += w
+			} else {
+				break
+			}
+		}
+	}
+
+	return input, len(input)
+}
+
+// Expand a single quoted string starting after a '\''
+func expandSingleQuoted(input string) (string, int) {
+	j := strings.Index(input, "'")
+	if j < 0 {
+		return input, len(input)
+	}
+	return input[:j], (j + 1)
+}
+
+// Expand something starting with at '$'.
+func expandSigil(input string, vars map[string][]string) (string, int) {
+    c, w := utf8.DecodeRuneInString(input)
+    var offset int
+    var varname string
+    if c == '{' {
+        j := strings.IndexRune(input[w:], '}')
+        if j < 0 {
+            return input, len(input)
+        }
+
+        varname = input[w:j]
+        offset = j + 1
+    } else {
+        // try to match a variable name
+        i := w
+        j := i
+        for j < len(input) {
+            c, w = utf8.DecodeRuneInString(input)
+            if !(isalpha(c) || c == '_' || (j > i && isdigit(c))) {
+                break
+            }
+            j += w
+        }
+
+        if j > i {
+            varname = input[i:j]
+        } else {
+            return input, len(input)
+        }
+    }
+
+    if isValidVarName(varname) {
+        varvals, ok := vars[varname]
+        if ok {
+            return strings.Join(varvals, " "), offset
+        }
+    }
+
+    return input, len(input)
+}
+
+
+// Find and expand all sigils.
+func expandSigils(input string, vars map[string][]string) string {
+    expanded := make([]byte, 0)
+    for i := 0; i < len(input); {
+        j := strings.IndexRune(input[i:], '$')
+        if j < 0 {
+            expanded = append(expanded, input[i:]...)
+            break
+        }
+
+        ex, k := expandSigil(input[j+1:], vars)
+        expanded = append(expanded, ex...)
+        i = k
+    }
+
+    return string(expanded)
+}
+
+
+
+// Expand all unescaped '%' characters.
+func expandSuffixes(input string, stem string) string {
+    expanded := make([]byte, 0)
+    for i := 0; i < len(input); {
+        j := strings.IndexAny(input[i:], "\\%")
+        if j < 0 {
+            expanded = append(expanded, input[i:]...)
+            break
+        }
+
+        c, w := utf8.DecodeRuneInString(input[j:])
+        if c == '%' {
+            expanded = append(expanded, stem...) 
+            i += w
+        } else {
+            j += w
+            c, w := utf8.DecodeRuneInString(input[j:])
+            if c == '%' {
+                expanded = append(expanded, '%')
+                i = j + w
+            }
+        }
+    }
+
+    return string(expanded)
+}
+
+
+// TODO: expand RegexpRefs
+
+
+// Expand a backtick quoted string, by executing the contents.
+func expandBackQuoted(input string, vars map[string][]string) (string, int) {
+    // TODO: expand sigils?
+	j := strings.Index(input, "`")
+	if j < 0 {
+		return input, len(input)
+	}
+
+	output := executeRecipe("sh", nil, input[:j], false, false, true)
+	return output, (j + 1)
+}
+
+