Fixed bug with field type and added program to disassemble a protobuf

.gitignore

@@ -7,3 +7,4 @@
 *.o
 .settings/language.settings.xml
 test_protobuf
+protobuf_reader

Makefile

@@ -10,11 +10,15 @@ OBJS = protobuf.o varint.o
 test_protobuf: $(OBJS)
 	$(CC) -o $@ $^ $(LFLAGS)
 
-all: $(OBJS)
+protobuf_reader: $(OBJS) main.o
+	$(CC) -o $@ $^ 
+
+all: protobuf_reader
 	cd test; make all;
 	
 clean:
 	rm -f *.o
+	rm -f protobuf_reader;
 	cd test; make clean;
 	
 rebuild: clean all

main.c

@@ -0,0 +1,120 @@
+#include <string.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "protobuf.h"
+
+/**
+ * opens a file to give a list of fields
+ */
+
+size_t os_utils_file_size(const char* path) {
+	size_t file_size = 0;
+	// open file
+	FILE* in_file = fopen(path, "r");
+	if (in_file == NULL)
+		return 0;
+	// determine size
+	fseek(in_file, 0L, SEEK_END);
+	file_size = ftell(in_file);
+	fclose(in_file);
+	return file_size;
+}
+
+char* getWireType(enum WireType type) {
+	switch(type) {
+		case(WIRETYPE_VARINT):
+			return "Varint";
+		case (WIRETYPE_LENGTH_DELIMITED):
+			return "Length Delimited";
+		case (WIRETYPE_64BIT):
+			return "64 Bit";
+		case (WIRETYPE_START_GROUP):
+			return "Start Group";
+		case (WIRETYPE_END_GROUP):
+			return "End Group";
+		case (WIRETYPE_32BIT):
+			return "32 Bit";
+	}
+	return "Wire Type Invalid";
+}
+
+void stripit(int argc, char** argv) {
+	char tmp[strlen(argv[argc])];
+	strcpy(tmp, &argv[argc][1]);
+	tmp[strlen(tmp)-1] = 0;
+	strcpy(argv[argc], tmp);
+	return;
+}
+
+void strip_quotes(int argc, char** argv) {
+	for(int i = 0; i < argc; i++) {
+		if (argv[i][0] == '\'' && argv[i][strlen(argv[i])-1] == '\'') {
+			stripit(i, argv);
+		}
+	}
+}
+
+int main(int argc, char** argv) {
+	strip_quotes(argc, argv);
+	if (argc <= 1) {
+		printf("Syntax: %s [filename] [start_pos]\n", argv[0]);
+		return 0;
+	}
+	char* fileName = argv[1];
+	size_t numBytes = os_utils_file_size(fileName);
+	printf("Number of bytes in file: %lu\n", numBytes);
+	if (numBytes == 0)
+		return 0;
+
+	FILE* file = fopen(fileName, "rb");
+	unsigned char buffer[numBytes];
+	if (fread(buffer, 1, numBytes, file) != numBytes) {
+		printf("Unexpected number of bytes.\n");
+		return 0;
+	}
+	//skip ahead
+	size_t skip = 0;
+	if (argc > 2) {
+		skip = atoi(argv[2]);
+		if (skip > 0) {
+			printf("Skipping first %lu bytes\n", skip);
+		}
+	}
+	int fieldCounter = 0;
+	size_t pos = skip;
+	while(pos < numBytes) {
+		size_t bytes_read = 0;
+		int field_no = 0;
+		enum WireType wire_type = WIRETYPE_64BIT;
+		if (protobuf_decode_field_and_type(&buffer[pos], numBytes - pos, &field_no, &wire_type, &bytes_read) == 0) {
+			printf("Unexpected return value from protobuf_decode_field_and_type at pos %lu\n", pos);
+			return 0;
+		}
+		printf("Field counter: %d at position %lu, Field Number: %d, Wire Type: %s", fieldCounter, pos, field_no, getWireType(wire_type));
+		pos += bytes_read;
+		// read the value
+		switch(wire_type) {
+			case(WIRETYPE_VARINT): {
+				unsigned long long varint = 0;
+				protobuf_decode_varint(&buffer[pos], numBytes-pos, &varint, &bytes_read);
+				pos += bytes_read;
+				printf(" Value: %llu\n", varint);
+				break;
+			}
+			case (WIRETYPE_LENGTH_DELIMITED): {
+				unsigned long long varint = 0;
+				protobuf_decode_varint(&buffer[pos], numBytes-pos, &varint, &bytes_read);
+				pos += bytes_read;
+				printf(" Field width: %llu. Next read position at %lu\n", varint, pos);
+				pos += varint;
+				break;
+			}
+			default:
+				pos++;
+		}
+		fieldCounter++;
+	}
+	return 0;
+}

protobuf.c

@@ -146,7 +146,7 @@ int protobuf_decode_field_and_type(const unsigned char* buffer, int buffer_lengt
 	*bytes_read = 0;
 	unsigned long long field = varint_decode(buffer, buffer_length, bytes_read);
 	*field_no = field >> 3;
-	*field_type = field & *field_no;
+	*field_type = field - (*field_no << 3);
 	return 1;
 }