common: add generic tokenization code

This is a little cleaner than passing around strings which are parsed
incrementally.

src/common/common.c

@@ -1,5 +1,6 @@
 #include <stdarg.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "common/common.h"
 
@@ -31,3 +32,80 @@ void downcase(char *str)
 		}
 	}
 }
+
+struct tokens {
+	struct token *next;
+	char *old;
+};
+
+struct token {
+	char *string;
+	struct token *next;
+};
+
+struct tokens* tokenize(const char *string, const char *delims)
+{
+	struct tokens *tokens = malloc(sizeof(*tokens));
+	struct token *token = malloc(sizeof(*token));
+	char *prev, *delim;
+	int done = 0;
+
+	tokens->next = token;
+	tokens->old = NULL;
+
+	while (!done) {
+		char *delim = strpbrk(prev, delims);
+		int has_token = 0;
+
+		/* No remaining delims, is there a token left? */
+		if (delim == NULL) {
+			has_token = strlen(prev) > 0;
+			done = 1;
+			break;
+		} else if (delim - string == 1) {
+			/* Adjacent delimiters, skip them */
+			prev = delim;
+			continue;
+		} else {
+			has_token = 1;
+		}
+
+		if (has_token) {
+			token->next = malloc(sizeof(struct tokens));
+			token->string = strndup(prev, delim - prev);
+			token = token->next;
+		}
+
+	}
+
+	if (tokens->next->string == NULL) {
+		free(tokens->next);
+		free(tokens);
+		return NULL;
+	} else {
+		free(token);
+		return tokens;
+	}
+}
+
+char *token_next(struct tokens* tokens)
+{
+	struct token *prev;
+
+	if (tokens->next) {
+		if (tokens->old) {
+			free(tokens->old);
+		}
+		tokens->old = tokens->next->string;
+
+		prev = tokens->next;
+		tokens->next = prev->next;
+		free(prev);
+
+		return tokens->old;
+	} else {
+		free(tokens->old);
+		free(tokens);
+		return NULL;
+	}
+}

src/common/common.h

@@ -16,6 +16,11 @@
  */
 void downcase(char *str);
 
+struct tokens;
+
+struct tokens* tokenize(const char *string, const char *delims);
+char *token_next(struct tokens* tokens);
+
 #ifdef DEBUG
 #define DEBUG_ON 1
 #else