read ttf font_directory

ttf.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <assert.h>

#include <arpa/inet.h>

#define READ_BE32(buf) htonl(*(u32 *)(buf->data + buf->offset)); buf->offset += 4
#define READ_BE16(buf) htons(*(u16 *)(buf->data + buf->offset)); buf->offset += 2

typedef uint64_t u64;
typedef uint32_t u32;
typedef uint16_t u16;
typedef uint8_t  u8;

typedef int64_t s64;
typedef int32_t s32;
typedef int16_t s16;
typedef int8_t  s8;

typedef float   f32;
typedef double  f64;

typedef struct buffer { u8 *data; u64 offset; u64 size; } buffer;

typedef struct offset_subtable { 
    u32 scaler_type;
	u16 num_tables;
	u16 search_range;
	u16 entry_selector;
	u16 range_shift;
} offset_subtable;

typedef struct table_directory {
    union { char tag_c[4]; u32 tag; };
	u32 checksum;
	u32 offset;
	u32 length;
} table_directory;

typedef struct font_directory { 
    offset_subtable off_sub; 
    table_directory *tbl_dir;  
} font_directory;

static buffer
read_file(char *filename)
{
    FILE *file = fopen(filename, "rb");
    buffer result = { 0 };
    
    if (file) {
        fseek(file, 0, SEEK_END);
        result.size = ftell(file);
        result.data = malloc(result.size);
        fseek(file, 0, SEEK_SET);
        fread(result.data, result.size, 1, file);
        fclose(file);
    }
    
    return(result);
}

static offset_subtable
read_offset_table(buffer *file)
{
    offset_subtable result;
    
    result.scaler_type = READ_BE32(file);
    result.num_tables = READ_BE16(file);
    result.search_range = READ_BE16(file);
    result.entry_selector = READ_BE16(file);
    result.range_shift = READ_BE16(file);
    
    return(result);
}

static table_directory *
read_table_directory(buffer *file, u16 table_count)
{
    table_directory *result = calloc(1, sizeof(table_directory) * table_count);
    
    for (int i = 0; i < table_count; ++i) {
        table_directory *td = result + i;
        td->tag = READ_BE32(file);
        td->checksum = READ_BE32(file);
        td->offset = READ_BE32(file);
        td->length = READ_BE32(file);
    }
    
    return(result);
}

static font_directory
read_font_directory(buffer *file)
{
    font_directory result;
    
    result.off_sub = read_offset_table(file);
    result.tbl_dir = read_table_directory(file, result.off_sub.num_tables);
    
    return(result);
}

int
main(int argc, char **argv)
{
    if (argc != 2) {
        fprintf(stderr, "[ERROR] Usage: %s filename\n", argv[0]);
        return(1);
    }
    
    buffer font_file = read_file(argv[1]);
    font_directory font_dir = read_font_directory(&font_file);
    
    return(0);
}