From a82fb28ede37a9e81cfca1b99b18c04746bcede5 Mon Sep 17 00:00:00 2001
From: Dmitry Mikhirev
Date: Mon, 17 Nov 2014 14:34:33 +0300
Subject: code comments

---
 GNUmakefile | 12 +++++++++++
 pcre.c      | 67 ++++++++++++++++++++++++++++++++-----------------------------
 2 files changed, 47 insertions(+), 32 deletions(-)

diff --git a/GNUmakefile b/GNUmakefile
index c4999b2..3557b15 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -14,11 +14,23 @@ pcre.so: pcre.c
 
 check: $(tests)
 
+
+### TEST EXPRESSIONS ###
+# each expression is passed to test(1)
+
+# simple test for pattern matching
 test001 = '$(m ^test$,test)' = test
+
+# test for pattern expansion
 test002: var = es
 test002 = '$(m ^t$(var)t$$,test,E)' = test
+
+# test for string capturing by number
 test003 = '$(m ^t(es)t$,test)$0$1' = testtestes -a -z '$(m a,b)$0$1'
 
+### END OF TEST EXPRESSIONS ###
+
+
 test%:
 	@if [ $($@) ] ; then \
 		echo '$@ PASSED'; \
diff --git a/pcre.c b/pcre.c
index aff9a3d..10fe267 100644
--- a/pcre.c
+++ b/pcre.c
@@ -24,53 +24,55 @@
 
 int plugin_is_GPL_compatible;
 
-const int MAX_CAP = 256;
+const int MAX_CAP = 256;   /* maximum number of substrings to capture */
+const int MAX_CAP_LEN = 3; /* number of decimal digits in MAX_CAP */
 
+/* match() - function to be attached to make pattern matching function */
 char *match(const char *name, int argc, char **argv)
 {
-	char *pat = NULL;
-	char *p;
-	int co = 0;
-	pcre *re;
-	const char *err;
-	int erroffset;
-	char *str = NULL;
-	int ncap = 0;
-	int ovec[MAX_CAP*3];
-	char *retstr = NULL;
-	int i;
+	char *pat = NULL;    /* expanded pattern */
+	char *p;             /* iteration pointer */
+	int co = 0;          /* pattern compilation options */
+	pcre *re;            /* compiled regexp */
+	const char *err;     /* compilation error */
+	int erroffset;       /* offset of pattern character whwre error occured */
+	char *str = NULL;    /* expanded subject string */
+	int ncap = 0;        /* number of captured substrings */
+	int ovec[MAX_CAP*3]; /* ovector */
+	char *retstr = NULL; /* string to be returned */
+	int i;               /* iterator */
 
-	if (argc > 2) {
+	if (argc > 2) { /* options provided, parse them */
 		for (p = argv[2]; *p != '\0'; p++) {
 			switch (*p) {
-			case 'E':
+			case 'E': /* expand pattern */
 				pat = gmk_expand(argv[0]);
 				break;
-			case 'i':
+			case 'i': /* ignore case */
 				co |= PCRE_CASELESS;
 				break;
-			case 'm':
+			case 'm': /* multi-line */
 				co |= PCRE_MULTILINE;
 				break;
-			case 's':
+			case 's': /* single-line */
 				co |= PCRE_DOTALL;
 				break;
-			case 'u':
+			case 'u': /* use Unicode properties */
 				co |= PCRE_UCP;
 				break;
-			case 'U':
+			case 'U': /* ungreedy quantifiers */
 				co |= PCRE_UNGREEDY;
 				break;
-			case 'x':
+			case 'x': /* extended regexp */
 				co |= PCRE_EXTENDED;
 				break;
-			case 'X':
+			case 'X': /* PCRE extras */
 				co |= PCRE_EXTRA;
 				break;
-			case '8':
+			case '8': /* UTF-8 */
 				co |= PCRE_UTF8;
 				break;
-			default:
+			default: /* unknown option */
 				fprintf(stderr, "%s: unknown option `%c'\n",
 						name, *p);
 				break;
@@ -78,40 +80,40 @@ char *match(const char *name, int argc, char **argv)
 		}
 	}
 
-	if (pat == NULL) {
+	if (pat == NULL) { /* compile unexpanded pattern */
 		re = pcre_compile(argv[0], 0, &err, &erroffset, NULL);
-	} else {
+	} else {           /* compile expanded pattern */
 		re = pcre_compile(pat, 0, &err, &erroffset, NULL);
 		gmk_free(pat);
 	}
-	if (re == NULL) {
+	if (re == NULL) { /* compilation error */
 		fprintf(stderr, "%s: %d: %s\n", name, erroffset, err);
 		goto end_match;
 	}
 
+	/* expand subject string and execute regexp */
 	str = gmk_expand(argv[1]);
-
 	ncap = pcre_exec(re, NULL, str, strlen(str), 0, 0, ovec, MAX_CAP*3);
 	pcre_free(re);
 
 end_match:
-	if (ncap) {
+	if (ncap) { /* set retstr to matched substring */
 		int len = ovec[1] - ovec[0];
 		retstr = gmk_alloc(len + 1);
 		strncpy(retstr, str + ovec[0], len);
 		retstr[len] = '\0';
 	}
-	for (i = 0; i < ncap; i++) {
+	for (i = 0; (i < ncap) && (i < MAX_CAP); i++) { /* set make vars to captured substrings */
 		char c = *(str + ovec[i*2 + 1]);
 		*(str + ovec[i*2 + 1]) = '\0';
 		int len = ovec[i*2 + 1] - ovec[i];
-		char mk_set[len + 18];
+		char mk_set[len + MAX_CAP_LEN + 16];
 		sprintf(mk_set, "define %d\n%s\nendef\n", i, str + ovec[i*2]);
 		*(str + ovec[i*2 + 1]) = c;
 		gmk_eval(mk_set, NULL);
 	}
-	for (; i < MAX_CAP; i++) {
-		char mk_set[14];
+	for (; i < MAX_CAP; i++) { /* udefine remaining make vars */
+		char mk_set[MAX_CAP_LEN + 11];
 		sprintf(mk_set, "undefine %d\n", i);
 		gmk_eval(mk_set, NULL);
 	}
@@ -123,6 +125,7 @@ end_match:
 
 int pcre_gmk_setup()
 {
+	/* add function for pattern matching */
 	gmk_add_function("pcre_find", (gmk_func_ptr)match, 2, 3, GMK_FUNC_NOEXPAND);
 	gmk_add_function("m", (gmk_func_ptr)match, 2, 3, GMK_FUNC_NOEXPAND);
 	return 1;
-- 
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