initial commit

.gitignore

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+.vs/
+
+[Oo]ut/
+[Bb]uild/
+
+*.json

CMakeLists.txt

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+# CMakeList.txt : Top-level CMake project file, do global configuration
+# and include sub-projects here.
+#
+cmake_minimum_required (VERSION 3.8)
+
+project ("jpeg-dissect")
+
+# Include sub-projects.
+add_subdirectory ("src")

src/CMakeLists.txt

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+cmake_minimum_required (VERSION 3.8)
+
+add_executable (jpeg-dissect 
+	"main.c"
+	"loader.c"
+ "util.h")

src/loader.c

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+#include "loader.h"
+
+#include <stdio.h>
+#include <stdint.h>
+
+#include "util.h"
+
+static int load_segment(FILE* fp);
+
+static int load_rst_segment(FILE* fp, uint8_t n);
+static int load_app_segment(FILE* fp, uint8_t n);
+
+static int load_app0_segment(FILE* fp);
+
+int load_jpeg(const char* filename)
+{
+	FILE* fp = fopen(filename, "r");
+	if (fp == NULL)
+	{
+		return 1;
+	}
+
+	while (!feof(fp))
+	{
+		if (load_segment(fp) != 0)
+		{
+			fprintf(stderr, "Segment loading failed\n");
+			return 1;
+		}
+	}
+
+	fclose(fp);
+	return 0;
+}
+
+int load_segment(FILE* fp)
+{
+	uint8_t segment_marker[2];
+	size_t segment_marker_size = sizeof(segment_marker);
+
+	if (fread(segment_marker, sizeof(uint8_t), segment_marker_size, fp) != segment_marker_size)
+	{
+		fprintf(stderr, "Marker terminated unexpectedly\n");
+		return 1;
+	}
+
+	if (segment_marker[0] != 0xFF)
+	{
+		fprintf(stderr, "Ill-formatted marker\n");
+		return 1;
+	}
+
+	// Handle special APPn/RSTn markers
+	if (segment_marker[1] >= 0xD0 && segment_marker[1] <= 0xD7)
+	{
+		if (load_rst_segment(fp, segment_marker[1] | 0x0F) != 0)
+		{
+			return 1;
+		}
+	}
+	else if ((segment_marker[1] & 0xF0) == 0xE0)
+	{
+		if (load_app_segment(fp, segment_marker[1] & 0x0F) != 0)
+		{
+			return 1;
+		}
+	}
+	else
+	{
+		switch (segment_marker[1])
+		{
+		case 0xD8:	// Start of image
+			DEBUG_LOG("SOI marker encountered");
+			break;
+
+		default:
+			fprintf(stderr, "Unimplemented marker 0xFF 0x%02X\n", segment_marker[1]);
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+int load_rst_segment(FILE* fp, uint8_t n)
+{
+	DEBUG_LOG("RST%d marker encountered", n);
+	return 1;
+}
+
+int load_app_segment(FILE* fp, uint8_t n)
+{
+	DEBUG_LOG("APP%d marker encountered", n);
+
+	switch (n)
+	{
+	case 0:	return load_app0_segment();
+
+	default: 
+		fprintf(stderr, "Unknown APP segment ID %d\n", n);
+		return 1;
+	}
+
+	return 0;
+}
+
+int load_app0_segment(FILE* fp)
+{
+
+}

src/loader.h

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+#ifndef _LODAER_H
+#define _LOADER_H
+
+int load_jpeg(const char* filename);
+
+#endif // _LOADER_H

src/main.c

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+#include <stdio.h>
+#include "loader.h"
+
+static void print_usage(void)
+{
+	printf("Usage: ./jpeg-dissect <JPEG file>\n");
+}
+
+int main(int argc, char** argv)
+{
+	if (argc != 2)
+	{
+		print_usage();
+		return 1;
+	}
+
+	const char* filename = argv[1];
+	printf("Supplied file: %s\n", filename);
+
+	if (load_jpeg(filename) != 0)
+	{
+		fprintf(stderr, "Failed to load jpeg\n");
+		return 1;
+	}
+
+	return 0;
+}

src/util.h

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+#ifndef _UTIL_H
+#define _UTIL_H
+
+#include <stdio.h>
+
+#ifdef NDEBUG
+#define DEBUG_LOG
+#else
+#define DEBUG_LOG(msg, ...) printf("[DEBUG] " ##msg "\n", __VA_ARGS__);
+#endif
+
+#endif // _UTIL_H