From 422b6c976e28445d2a6e14586fa416b0f16c093f Mon Sep 17 00:00:00 2001
From: Kimplul <kimi.h.kuparinen@gmail.com>
Date: Sat, 24 Jun 2023 20:48:32 +0300
Subject: initial commit

---
 lib/prune.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 lib/prune.c

(limited to 'lib/prune.c')

diff --git a/lib/prune.c b/lib/prune.c
new file mode 100644
index 0000000..5bf5f0b
--- /dev/null
+++ b/lib/prune.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void usage(const char *name)
+{
+	printf("Usage: %s <filter> <file>\n", name);
+}
+
+static size_t file_size(FILE *file)
+{
+	fseek(file, 0, SEEK_END);
+	size_t size = ftell(file);
+	rewind(file);
+	return size;
+}
+
+static char *read_file(FILE *file, size_t bytes)
+{
+	char *buf = malloc(bytes);
+	fread(buf, bytes, 1, file);
+	rewind(file);
+	return buf;
+}
+
+static int try_filter(FILE *filter, FILE *file)
+{
+	size_t filtsize = file_size(filter);
+	char *filtbuf = read_file(filter, filtsize);
+
+	size_t filsize = file_size(file);
+	char *filbuf = read_file(file, filsize);
+
+	// inform the user?
+	if (filsize < filtsize) {
+		free(filtbuf);
+		free(filbuf);
+		return 0;
+	}
+
+	size_t off = filsize - filtsize;
+	if (strncmp(filbuf + off, filtbuf, filtsize) != 0) {
+		// filter didn't match
+		free(filtbuf);
+		free(filbuf);
+		return 0;
+	}
+
+	// write everything except filtered part back to file
+	freopen(NULL, "w+", file);
+	fwrite(filbuf, off, 1, file);
+	free(filtbuf);
+	free(filbuf);
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	if (argc != 3) {
+		usage(argv[0]);
+		return -1;
+	}
+
+	FILE *filter = fopen(argv[1], "r");
+	if (!filter) {
+		fprintf(stderr, "failed opening filter file %s\n", argv[1]);
+		return -1;
+	}
+
+	FILE *file = fopen(argv[2], "r");
+	if (!file) {
+		fprintf(stderr, "failed opening file %s\n", argv[2]);
+		fclose(filter);
+		return -1;
+	}
+
+	int ret = try_filter(filter, file);
+
+	fclose(filter);
+	fclose(file);
+	return ret;
+}
-- 
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