Move all awk functions to separate files

awk/mask_plain.awk

@@ -0,0 +1,52 @@
+function find_unescaped_tag(s, tag,    p, off, pos) {
+    p = 1
+    while (1) {
+        off = index(substr(s, p), tag)
+        if (off == 0) return 0
+        pos = p + off - 1
+        if (pos == 1 || substr(s, pos - 1, 1) != "\\") return pos
+        p = pos + 1
+    }
+}
+
+function mask_plain(s,    t) {
+    t = s
+    gsub(/\*/, "\034P0\034", t)
+    gsub(/_/, "\034P1\034", t)
+    gsub(/`/, "\034P2\034", t)
+    gsub(/\[/, "\034P3\034", t)
+    gsub(/\]/, "\034P4\034", t)
+    gsub(/\(/, "\034P5\034", t)
+    gsub(/\)/, "\034P6\034", t)
+    gsub(/!/, "\034P7\034", t)
+    gsub(/\$/, "\034P8\034", t)
+    return t
+}
+BEGIN { in_plain = 0 }
+{
+    line = $0
+    out = ""
+    while (1) {
+        if (!in_plain) {
+            pos = find_unescaped_tag(line, "<plain>")
+            if (pos == 0) {
+                out = out line
+                break
+            }
+            out = out substr(line, 1, pos - 1) "<mfmplain>"
+            line = substr(line, pos + 7)
+            in_plain = 1
+        } else {
+            pos = find_unescaped_tag(line, "</plain>")
+            if (pos == 0) {
+                out = out mask_plain(line)
+                line = ""
+                break
+            }
+            out = out mask_plain(substr(line, 1, pos - 1)) "</mfmplain>"
+            line = substr(line, pos + 8)
+            in_plain = 0
+        }
+    }
+    print out
+}