Add parsing of magic number

src/Makefile.am

@@ -1,21 +1,11 @@
 NULL =
 
-bin_PROGRAMS = hvif
+	bin_PROGRAMS = hvif
 
-# veriT configuration
-hvif_CPPFLAGS = \
-	$(AM_CPPFLAGS) \
-	-I$(top_builddir)/src \
-	$(NULL)
-hvif_LDADD = \
-	$(AM_LDADD) \
-	-lm \
-	$(NULL)
-
-hvif_SOURCES = \
-	$(BUILT_SOURCES) \
-	src/main.c \
-	src/hvif-light.c \
-	src/hvif-light.h \
-	$(NULL)
+#veriT configuration
+		hvif_CPPFLAGS = $(AM_CPPFLAGS) - I$(top_builddir) / src $(NULL) hvif_LDADD =
+											$(AM_LDADD) -
+	lm $(NULL)
 
+		hvif_SOURCES = $(BUILT_SOURCES) src / main.c src / hvif -
+	light.c src / hvif - light.h $(NULL)

src/hvif-light.c

@@ -1,5 +1,44 @@
 #include "hvif-light.h"
 
-unsigned test(unsigned x) {
-	return 2*x;
+#include <stdint.h>
+#include <stdlib.h>
+
+char const* const eof_error = "File ended prematurely.";
+
+#define le_read(V, BUFFER) V = _Generic((V), uint32_t : le_read_uint32)(BUFFER)
+static inline uint32_t
+le_read_uint32(char buffer[static 1])
+{
+	return (buffer[0] << 0) | (buffer[1] << 8) | (buffer[2] << 16) |
+		(buffer[3] << 24);
+}
+
+#define ERROR_RESULT(M) \
+	(hvif_result) { .success = false, .error = M }
+
+struct hvif_image
+{};
+
+hvif_result
+hvif_from_file(FILE* file)
+{
+	uint32_t const magic = 0x6669636e; /* 'finc' (on disk little endian 'cnif') */
+
+	char magic_buffer[4];
+	if (fread(magic_buffer, 1, 4, file) != 4) { return ERROR_RESULT(eof_error); }
+	uint32_t read_magic;
+	le_read(read_magic, magic_buffer);
+	if (read_magic != magic) {
+		printf("%04x %04x\n", magic, read_magic);
+		return ERROR_RESULT("Wrong magic number.");
+	}
+
+	hvif_image* image = malloc(sizeof(hvif_image));
+	return (hvif_result){ .success = true, .image = image };
+}
+
+void
+hvif_free(hvif_image* image)
+{
+	free(image);
 }

src/hvif-light.h

@@ -1,7 +1,23 @@
 #ifndef HVIF_LIGHT_H
 #define HVIF_LIGHT_H
 
-unsigned test(unsigned x);
+#include <stdbool.h>
+#include <stdio.h>
+
+typedef struct hvif_image hvif_image;
+
+typedef struct hvif_result hvif_result;
+struct hvif_result
+{
+	bool success;
+	union
+	{
+		char const* const error;
+		hvif_image* image;
+	};
+};
+
+hvif_result hvif_from_file(FILE* file);
+void hvif_free(hvif_image* image);
 
 #endif // HVIF_LIGHT_H
-

src/main.c

@@ -1,13 +1,29 @@
-#include <stdio.h>
-#include <stdlib.h>
-
 #include "config.h"
 #include "hvif-light.h"
 
-int main(void) {
-	unsigned x = 12;
-	unsigned y = test(x);
-	printf("This is " PACKAGE_STRING " and 2*%u = %u.\n", x, y);
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+main(void)
+{
+	puts("This is " PACKAGE_STRING ".");
+
+	FILE* imagefile = fopen("test.hvif", "r");
+	if (!imagefile) {
+		fputs("fopen failed.\n", stderr);
+		return EXIT_FAILURE;
+	}
+
+	hvif_result result = hvif_from_file(imagefile);
+	if (!result.success) {
+		fputs("Reading image failed.\n", stderr);
+		fputs(result.error, stderr);
+		fputc('\n', stderr);
+		return EXIT_FAILURE;
+	}
+	puts("Reading image succeeded.");
+	hvif_free(result.image);
 
 	return EXIT_SUCCESS;
 }