Minor refactoring. Update throwaway size info and make it possible to change

huffman.c

@@ -7,36 +7,9 @@
 #include "header.h"
 #include "print_helper.h"
 
-#define HUFFMAN_START 3
-
-void free_tree(struct tree *parent)
-{
-	if (parent == NULL)
-		return;
-
-	free_tree(parent->left);
-	free_tree(parent->right);
-
-	free(parent);
-}
-
-long get_file_size(FILE *file)
-{
-	long pos = ftell(file);
-	fseek(file, 0, SEEK_END);
-	long size = ftell(file);
-	fseek(file, pos, SEEK_SET);
-	return size;
-}
-
-/* free it yourself faget. */
-char *read_text(FILE *file, long size)
-{
-	char *buf = malloc(size + 1);
-	fread(buf, size, 1, file);
-	buf[size] = '\0';
-	return buf;
-}
+/* The first bits that are reserved for throwaways. The throwaways indicates the
+ * number of bits to throw away at the end when decoding the file. */
+#define THROWAWAY_SIZE 3
 
 int insert_throwaways(FILE *file, unsigned char throwaways)
 {
@@ -47,9 +20,9 @@ int insert_throwaways(FILE *file, unsigned char throwaways)
 	fseek(file, 0, SEEK_SET);
 	fread(&firstbyte, sizeof(firstbyte), 1, file);
 
-	throwaways &= 0x7;
+	throwaways &= 0xff >> (8 - THROWAWAY_SIZE);
 
-	firstbyte |= (throwaways << 5);
+	firstbyte |= (throwaways << (8 - THROWAWAY_SIZE));
 
 	fseek(file, 0, SEEK_SET);
 	fwrite(&firstbyte, sizeof(firstbyte), 1, file);
@@ -68,22 +41,51 @@ unsigned char read_throwaways(FILE *file)
 	fseek(file, 0, SEEK_SET);
 	fread(&firstbyte, sizeof(firstbyte), 1, file);
 
-	firstbyte >>= 5;
-	firstbyte &= 0x7;
+	firstbyte >>= 8 - THROWAWAY_SIZE;
+	firstbyte &= 0xff >> (8 - THROWAWAY_SIZE);
 
 	fseek(file, filepos, SEEK_SET);
 
 	return firstbyte;
 }
 
-int encode_file(FILE *in, FILE *out)
+long get_file_size(FILE *file)
+{
+	long pos = ftell(file);
+	fseek(file, 0, SEEK_END);
+	long size = ftell(file);
+	fseek(file, pos, SEEK_SET);
+	return size;
+}
+
+static void free_tree(struct tree *parent)
+{
+	if (parent == NULL)
+		return;
+
+	free_tree(parent->left);
+	free_tree(parent->right);
+
+	free(parent);
+}
+
+/* free it yourself faget. */
+static char *read_text(FILE *file, long size)
+{
+	char *buf = malloc(size + 1);
+	fread(buf, size, 1, file);
+	buf[size] = '\0';
+	return buf;
+}
+
+static int encode_file(FILE *in, FILE *out)
 {
 	struct tree *tree;
 	struct BIT_BUFFER bitbuf;
 	bb_init(&bitbuf, out);
 
 	/* Make room for throwaways right now. */
-	bitbuf.pos += HUFFMAN_START;
+	bitbuf.pos += THROWAWAY_SIZE;
 
 	long size = get_file_size(in);
 
@@ -106,13 +108,13 @@ int encode_file(FILE *in, FILE *out)
 	bb_flush(&bitbuf);
 }
 
-int decode_file(FILE *in, FILE *out)
+static int decode_file(FILE *in, FILE *out)
 {
 	struct tree *tree = malloc(sizeof(*tree));
 	struct BIT_BUFFER bitbuf;
 	bb_init(&bitbuf, in);
 
-	bitbuf.pos += HUFFMAN_START;
+	bitbuf.pos += THROWAWAY_SIZE;
 
 	fseek(in, 0, SEEK_SET);
 	decode_header(&bitbuf, tree);