#include "fat12.h"


void fat12_write_u8(void *ptr, uint8_t val) {
    ((uint8_t *)ptr)[0] = (val >> 0) & 0xff;
}

uint8_t fat12_read_u8(void *ptr) {
    uint16_t val = 0;
    val |= (((uint8_t *)ptr)[0] << 0) & 0xff;
    return val;
}

void fat12_write_u16(void *ptr, uint16_t val) {
    ((uint8_t *)ptr)[0] = (val >> 0) & 0xff;
    ((uint8_t *)ptr)[1] = (val >> 8) & 0xff;
}

uint16_t fat12_read_u16(void *ptr) {
    uint16_t val = 0;
    val |= (((uint8_t *)ptr)[0] << 0) & 0x00ff;
    val |= (((uint8_t *)ptr)[1] << 8) & 0xff00;
    return val;
}

void fat12_set_cluster(void *fat, uint32_t cluster, uint32_t value) {
    uint32_t offset = (cluster * 3) / 2;
    if (cluster&1) {
        ((uint8_t *)fat)[offset] = (((uint8_t *)fat)[offset] & 0x0f) | ((value << 4) & 0xf0);
        ((uint8_t *)fat)[offset + 1] = value >> 4;
    }
    else {
        ((uint8_t *)fat)[offset] = value;
        ((uint8_t *)fat)[offset + 1] = (((uint8_t *)fat)[offset] & 0xf0) | ((value >> 8) & 0x0f);
    }
}

uint32_t fat12_get_cluster(void *fat, uint32_t cluster) {
    uint32_t offset = (cluster * 3) / 2;
    uint32_t value = 0;

    if (cluster&1) {
        value |= (((uint8_t *)fat)[offset] >> 4) & 0x00f;
        value |= (((uint8_t *)fat)[offset + 1] << 4) & 0xff0;
    }
    else {
        value |= ((uint8_t *)fat)[offset];
        value |= (((uint8_t *)fat)[offset + 1] << 8) & 0xf00;
    }

    return value;
}