Add throwaways as first 3 bits

This allows the last byte to be interpreted correctly, by not allowing the
cursor to move further than the max bits to read.

huffman.c

@@ -7,6 +7,8 @@
 #include "header.h"
 #include "print_helper.h"
 
+#define HUFFMAN_START 3
+
 void free_tree(struct tree *parent)
 {
 	while (parent != NULL) {
@@ -41,12 +43,54 @@ char *read_text(FILE *file, long size)
 	return buf;
 }
 
+int insert_throwaways(FILE *file, unsigned char throwaways)
+{
+	long filepos = ftell(file);
+
+	unsigned char firstbyte;
+
+	fseek(file, 0, SEEK_SET);
+	fread(&firstbyte, sizeof(firstbyte), 1, file);
+
+	throwaways &= 0x7;
+
+	firstbyte |= (throwaways << 5);
+	printb(firstbyte);
+
+	fseek(file, 0, SEEK_SET);
+	fwrite(&firstbyte, sizeof(firstbyte), 1, file);
+
+	fseek(file, filepos, SEEK_SET);
+
+	return 0;
+}
+
+unsigned char read_throwaways(FILE *file)
+{
+	long filepos = ftell(file);
+
+	unsigned char firstbyte;
+
+	fseek(file, 0, SEEK_SET);
+	fread(&firstbyte, sizeof(firstbyte), 1, file);
+
+	firstbyte >>= 5;
+	firstbyte &= 0x7;
+
+	fseek(file, filepos, SEEK_SET);
+
+	return firstbyte;
+}
+
 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;
+
 	long size = get_file_size(in);
 
 	fseek(in, 0, SEEK_SET);
@@ -77,6 +121,8 @@ int decode_file(FILE *in, FILE *out)
 	struct BIT_BUFFER bitbuf;
 	bb_init(&bitbuf, in);
 
+	bitbuf.pos += HUFFMAN_START;
+
 	fseek(in, 0, SEEK_SET);
 	decode_header(&bitbuf, tree);
 
@@ -131,7 +177,7 @@ int main(int argc, char *argv[])
 		return -1;
 	}
 
-	FILE *output = fopen(outfile, "w");
+	FILE *output = fopen(outfile, "w+");
 	if (!output) {
 		fprintf(stderr, "Failed to open output file\n");
 		fclose(input);

tree.c

 
 #include <stdlib.h>
 
+#include "huffman.h"
 #include "tree.h"
 
 /* The character set we support */
@@ -136,6 +137,8 @@ int encode_tree(struct BIT_BUFFER *bitbuf, struct tree *parent, char *buf,
 		write_entry(bitbuf, parent, buf[i]);
 	}
 
+	insert_throwaways(bitbuf->fp, 8 - bitbuf->pos);
+
 	return 0;
 }
 
@@ -143,8 +146,16 @@ static int read_entries(struct BIT_BUFFER *bitbuf, FILE *out,
 						struct tree *parent)
 {
 	int *bit;
+	int bitsread = 0;
+
+	int totalbits = get_file_size(bitbuf->fp) * 8;
+	int huffmanbits = totalbits - read_throwaways(bitbuf->fp);
+
+	printf("Total bits to parse %d\n", huffmanbits);
+
 	struct tree *leaf = parent;
 	while ((bit = bb_read(bitbuf, 1)) != NULL) {
+
 		if (*bit == 1) {
 			fwrite(&leaf->right->ch, 1, 1, out);
 			leaf->right->freq++;
@@ -158,6 +169,11 @@ static int read_entries(struct BIT_BUFFER *bitbuf, FILE *out,
 			}
 		}
 		free(bit);
+
+		if (bitsread == huffmanbits)
+			break;
+
+		bitsread++;
 	}
 
 	return 0;