fzy

commit c38e32f36780a5bc45b879e8db3f84778e3de8ab
parent 99f9e472e77de68533fa1c150bcab6bc86235582
Author: John Hawthorn <john.hawthorn@gmail.com>
Date:   Thu, 21 Apr 2016 11:12:15 -0700

Read entire input into contiguous memory

This should be slightly faster at loading the input into memory, since
fewer mallocs will be required vs running one malloc per-line of input.

Realloc on modern systems is fast. It can use mremap internally to remap
virtual memory pages and avoid copying. This can be seen in strace. Neat!

I thought that this might be friendlier to caching, but there was no
noticeable differnce when scanning through the strings for matches. It's
probable that the previous strdups placed them more-or-less contiguously
and the extra padding for malloc bookkeeping didn't make a significant
differnce. This also suggests that alignment of the candidate strings
wasn't important.

Diffstat:
M
fzy.c
 | 
39
+++++++++++++++++++++++++++------------

1 file changed, 27 insertions(+), 12 deletions(-)
diff --git a/fzy.c b/fzy.c
@@ -19,19 +19,34 @@ static size_t scrolloff = 1;
 static const char *prompt = "> ";
 
 static void read_choices(choices_t *c) {
-	const char *line;
-	char buf[4096];
-	while (fgets(buf, sizeof buf, stdin)) {
-		char *nl;
-		if ((nl = strchr(buf, '\n')))
-			*nl = '\0';
-
-		if (!(line = strdup(buf))) {
-			fprintf(stderr, "Cannot allocate memory");
-			abort();
-		}
-		choices_add(c, line);
+	size_t bufsize = 65536;
+	size_t pos = 0;
+	size_t sizeread;
+
+	/* Read entire file into contiguous memory buffer */
+	char *buf = malloc(bufsize);
+	while ((sizeread = fread(buf + pos, 1, bufsize - pos, stdin))) {
+		pos += sizeread;
+		bufsize *= 2;
+		buf = realloc(buf, bufsize);
 	}
+	buf = realloc(buf, pos + 1);
+
+	buf[pos] = 0;
+
+	/* Tokenize input and add to choices */
+	char *line = buf;
+	do {
+		char *nl = strchr(line, '\n');
+		if (nl)
+			*nl++ = '\0';
+
+		/* Skip empty lines */
+		if (*line)
+			choices_add(c, line);
+
+		line = nl;
+	} while (line);
 }
 
 #define SEARCH_SIZE_MAX 4096