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Code Issues Releases Activity

OP-452: Made the CRC calculation run in chunks to balance efficiency and ram

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usage, because Stac caught me being lazy :)
This commit is contained in:
James Cotton 2011-06-05 09:05:33 -05:00
parent e02aa1b818
commit 0a56129b35
1 changed files with 11 additions and 8 deletions
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19
flight/PiOS/Common/pios_flashfs_objlist.c
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@ -254,8 +254,11 @@ int32_t PIOS_FLASHFS_ObjSave(UAVObjHandle obj, uint16_t instId, uint8_t * data)
int32_t PIOS_FLASHFS_ObjLoad(UAVObjHandle obj, uint16_t instId, uint8_t * data)
{
uint32_t objId = UAVObjGetID(obj);
uint16_t objSize = UAVObjGetNumBytes(obj);
uint8_t crc = 0;
uint8_t crcFlash = 0;
const uint8_t crc_read_step = 8;
uint8_t crc_read_buffer[crc_read_step];
int32_t addr = PIOS_FLASHFS_GetObjAddress(objId, instId);
@ -276,23 +279,23 @@ int32_t PIOS_FLASHFS_ObjLoad(UAVObjHandle obj, uint16_t instId, uint8_t * data)
if((header.id != objId) || (header.instId != instId))
return -3;
// To avoid having to allocate the RAM for a copy of the object, we read once bytewise
// and compute the CRC (inefficient)
for(uint32_t i = 0; i < UAVObjGetNumBytes(obj); i++) {
uint8_t byte;
PIOS_Flash_W25X_ReadData(addr + sizeof(header) + i, &byte, 1);
crc = PIOS_CRC_updateByte(crc, byte);
// To avoid having to allocate the RAM for a copy of the object, we read by chunks
// and compute the CRC
for(uint32_t i = 0; i < objSize; i += crc_read_step) {
PIOS_Flash_W25X_ReadData(addr + sizeof(header) + i, crc_read_buffer, crc_read_step);
uint8_t valid_bytes = ((i + crc_read_step) >= objSize) ? objSize - i : crc_read_step;
crc = PIOS_CRC_updateCRC(crc, crc_read_buffer, valid_bytes);
}
// Read CRC (written so will work when CRC changes to uint16)
if(PIOS_Flash_W25X_ReadData(addr + sizeof(header) + UAVObjGetNumBytes(obj), (uint8_t *) &crcFlash, sizeof(crcFlash)) != 0)
if(PIOS_Flash_W25X_ReadData(addr + sizeof(header) + objSize, (uint8_t *) &crcFlash, sizeof(crcFlash)) != 0)
return -5;
if(crc != crcFlash)
return -6;
// Read the instance data
if (PIOS_Flash_W25X_ReadData(addr + sizeof(header), data, UAVObjGetNumBytes(obj)) != 0)
if (PIOS_Flash_W25X_ReadData(addr + sizeof(header), data, objSize) != 0)
return -4;
return 0;