porklib: Simple library for programming Arduino in C
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avr-lib/lib/sd_blockdev.c

185 lines
2.8 KiB

#include <stdint.h>
#include <stdbool.h>
#include "sd_blockdev.h"
#include "sd.h"
// helpers
void load_sector(const uint32_t addr);
void store_sector();
void handle_cursor_ov();
// blockdev methods
void dev_load(void* dest, const uint16_t len);
void dev_store(const void* src, const uint16_t len);
uint8_t dev_read();
void dev_write(const uint8_t b);
void dev_seek(const uint32_t addr);
void dev_rseek(const int16_t offset);
void dev_flush();
/** Sector buffer */
uint8_t buff[512];
/** Address of the buffered sector */
uint32_t buff_addr;
/** Buffer needs to be flushed before next read */
bool buff_dirty = false;
/** Buffer holds a valid sector */
bool buff_valid = false;
/** seek cursor */
uint32_t cursor_sec;
uint16_t cursor_offs;
/** Flush the buffer, if it's dirty */
void dev_flush()
{
if (buff_dirty)
{
store_sector();
buff_dirty = false;
}
}
void load_sector(const uint32_t addr)
{
// do not load if already loaded
if (buff_valid && buff_addr == addr)
{
return;
}
dev_flush();
// read entire sector
sd_read(addr, 0, buff, 0, 512);
buff_valid = true;
buff_addr = addr;
}
void store_sector()
{
// Do not store if not laoded.
if (!buff_dirty) return;
if (!buff_valid) return;
sd_write(buff_addr, buff);
}
/**
* Handle cursor overflow.
* MUST ABSOLUTELY NOT load/store buffer or change buffer addr!
*/
inline void handle_cursor_ov()
{
if (cursor_offs >= 512)
{
cursor_sec++;
cursor_offs = 0;
}
}
void dev_write(const uint8_t b)
{
load_sector(cursor_sec);
// dirty only if changed
if (buff[cursor_offs] != b)
{
buff[cursor_offs++] = b;
buff_dirty = true;
}
else
{
cursor_offs++;
}
handle_cursor_ov();
}
uint8_t dev_read()
{
load_sector(cursor_sec);
const uint8_t b = buff[cursor_offs++];
handle_cursor_ov();
return b;
}
void dev_load(void* dest, const uint16_t len)
{
for (uint16_t a = 0; a < len; a++)
{
*((uint8_t*)dest++) = dev_read();
}
}
void dev_store(const void* src, const uint16_t len)
{
for (uint16_t a = 0; a < len; a++)
{
dev_write(*((uint8_t*)src++));
}
}
void dev_seek(const uint32_t addr)
{
// compute sector and offset counters
cursor_sec = addr >> 9;
cursor_offs = addr & 0x1FF;
}
void dev_rseek(const int16_t offset)
{
// add WITHIN the same sector
if (offset > 0 && cursor_offs + offset < 512)
{
cursor_offs += offset;
return;
}
// subtract WITHIN the same sector
if (offset < 0 && ((uint16_t)(-offset) <= cursor_offs))
{
cursor_offs += offset;
return;
}
// abs addr change
dev_seek(((cursor_sec << 9) + cursor_offs) + offset);
}
/** Init SD card block device */
bool sdb_init(BLOCKDEV* dev)
{
if (!sd_init()) return false;
dev->load = &dev_load;
dev->store = &dev_store;
dev->read = &dev_read;
dev->write = &dev_write;
dev->seek = &dev_seek;
dev->rseek = &dev_rseek;
dev->flush = &dev_flush;
return true;
}