EC Interfaces

Interface Description

EC encoding and decoding interfaces.

Interface Format

int KsalEcEncode(uint8_t **data, uint8_t **parity, struct HecParam *param);
int KsalEcDecode(uint8_t **data, uint8_t **parity, struct HecParam *param);
int KsalLrcEncode(uint8_t **data, uint8_t **parity, struct LrcParam *param);
int KsalLrcDecode(uint8_t **data, uint8_t **parity, struct LrcParam *param);
int KsalLrcMininumToDecode(uint8_t *minimumToReadBitMap, uint8_t *availChunksBitMap, struct LrcParam *param, uint8_t minimumToReadBitMapLen, uint8_t availChunksBitMapLen);

KsalLrcEncode, KsalLrcDecode, and KsalLrcMinimumToDecode support only the 28+3 configuration.

Parameters

Parameter	Type	Description	Input/Output
data	Pointer array	Indicates the pointer array of the data blocks.	Input/Output
parity	Pointer array	Indicates the pointer array of the parity blocks.	Input/Output
param	Pointer to encoding and decoding parameters	Indicates the pointer to encoding and decoding parameters.	Input
minimumToReadBitMap	Pointer array	Indicates the minimum chunk bitmap information to be read.	Input/Output
availChunksBitMap	Pointer array	Indicates the bitmap information of available chunks.	Input
minimumToReadBitMapLen	Integer	Indicates the length of the minimumToReadBitMap array.	Input
availChunksBitMapLen	Integer	Indicates the length of the availChunksBitMap array.	Input
ret	Integer	Outputs 0 (success) or other values (failure).	Output

Data Structures

**Table 1** struct HecParam
Member	Type	Description
dataNum	Integer	Indicates the number of data blocks.
parityNum	Integer	Indicates the number of parity blocks.
sectorSize	Integer	Indicates the sector size, which is the minimum granularity for encoding and decoding. Currently, 64 bytes and 4,096 bytes are supported.
blockSize	Integer	Indicates the size of a data block or parity block. The value must be an integer multiple of sectorSize.
targetColNum	Integer	Indicates the number of lost blocks, which is used by the decoding interface.
targetColArray[6]	Integer	Indicates the list of lost blocks. The value range of each entry is [0, dataNum + parityNum).
version	Integer	Indicates the algorithm version and defaults to 1. 0: The sector size should be an integer multiple of 64 bytes (2 ≤ Number of data blocks ≤ 25, 1 ≤ Number of parity blocks ≤ 4). 1: The sector size should be an integer multiple of 4,096 bytes (2 ≤ Number of data blocks ≤ 25, 1 ≤ Number of parity blocks ≤ 4). 2: The sector size should be an integer multiple of 64 bytes (only the 6+3 configuration is supported).

**Table 2** struct LrcParam
Member	Type	Description
dataNum	Integer	Indicates the number of data blocks.
localParityNum	Integer	Indicates the number of local parity blocks.
globalParityNum	Integer	Indicates the number of global parity blocks.
sectorSize	Integer	Indicates the sector size, which is the minimum granularity for encoding and decoding. Currently, 64 bytes and 4,096 bytes are supported.
blockSize	Integer	Indicates the size of a data block or parity block. The value must be an integer multiple of sectorSize.
targetColNum	Integer	Indicates the number of lost blocks, which is used by the decoding interface.
targetColArray[6]	Integer	Indicates the list of lost blocks. The value range of each entry is [0, dataNum + parityNum).
version	Integer	Indicates the algorithm version and defaults to 1. 0: The sector size should be an integer multiple of 64 bytes. 1: The sector size should be an integer multiple of 4,096 bytes.

struct HecParam supports configurations other than 28+3, and struct LrcParam supports only the 28+3 configuration.

Dependency

ksal/ksal_erasure_code.h

Example

EC encoding and decoding interfaces (for configurations other than 28+3)

Write EC test code.

Create a test.c file.
1
vi test.c

Press i to enter the insert mode and add the following test code to the file:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ksal/ksal_erasure_code.h>

int main(int argc, char **argv)
{
    struct HecParam param = {4, 2, 4096, 8192, 2, {3, 4}};
    uint8_t tmp[20][8192];
    uint8_t *ptrs[20];
    uint8_t *bptrs[20];
    for (size_t i = 0; i < param.dataNum + param.parityNum; ++i) {
        for (size_t j = 0; j < param.blockSize; j++) {
                tmp[i][j] = (uint8_t)rand() & 0xff;
        }
        ptrs[i] = tmp[i];
        bptrs[i] = tmp[i];
    }
    KsalEcEncode(ptrs, ptrs + param.dataNum, &param);
    bptrs[3] = tmp[18];
    bptrs[4] = tmp[19];
    KsalEcDecode(bptrs, bptrs + param.dataNum, &param);
    if (memcmp(bptrs[3], ptrs[3], param.blockSize) == 0 &&
        memcmp(bptrs[4], ptrs[4], param.blockSize) == 0) {
        printf("decode succ!!\r\n");
    } else {
        printf("decode fail!!\r\n");
    }
    return 0;
}

Press Esc to exit the insert mode. Type :wq! and press Enter to save and exit the file.

Compile the test.c file into an executable file test.
1
gcc test.c -lksal -o test
Run the test executable file.
1
./test
The command output is as follows:
1
decode succ!!

EC encoding and decoding interfaces (for the 28+3 configuration)

Write EC test code.

Create a test.c file.
1
vi test.c

Press i to enter the insert mode and add the following test code to the file:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ksal/ksal_erasure_code.h>

int main(int argc, char **argv)
{
    struct LrcParam param = {28, 2, 1, 4096, 8192, 2, {3, 4}, 1};
    uint8_t tmp[40][8192];
    uint8_t *ptrs[40];
    uint8_t *bptrs[40];
    for (size_t i = 0; i < param.dataNum + param.localParityNum + param.globalParityNum; ++i) {
        for (size_t j = 0; j < param.blockSize; j++) {
                tmp[i][j] = (uint8_t)rand() & 0xff;
        }
        ptrs[i] = tmp[i];
        bptrs[i] = tmp[i];
    }
    KsalLrcEncode(ptrs, ptrs + param.dataNum, &param);
    bptrs[3] = tmp[32];
    bptrs[4] = tmp[33];
    KsalLrcDecode(bptrs, bptrs + param.dataNum, &param);
    if (memcmp(bptrs[3], ptrs[3], param.blockSize) == 0 &&
        memcmp(bptrs[4], ptrs[4], param.blockSize) == 0) {
        printf("decode succ!!\r\n");
    } else {
        printf("decode fail!!\r\n");
    }
    return 0;
}

Press Esc to exit the insert mode. Type :wq! and press Enter to save and exit the file.

Compile the test.c file into an executable file test.
1
gcc test.c -lksal -o test
Run the test executable file.
1
./test
The command output is as follows:
1
decode succ!!

EC interfaces that can select decoding positions based on the position of the erasure block (for the 28+3 configuration)

Write EC test code.

Create a test.c file.
1
vi test.c

Press i to enter the insert mode and add the following test code to the file:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ksal/ksal_erasure_code.h>

int main(int argc, char **argv)
{
    struct LrcParam param = {28, 2, 1, 4096, 8192, 2, {3, 4}, 1};
    uint8_t minimumToReadBitMapLen = 31;
    uint8_t availChunksBitMapLen = 31;
    uint8_t minimumToReadBitMap[31] = {0};
    uint8_t availChunksBitMap[31] = {0};
    for (size_t i = 0; i < param.dataNum + param.localParityNum + param.globalParityNum; ++i) {
        if (i != 3 && i != 4) {
            availChunksBitMap[i] = 1;
        }
    }
    int ret = KsalLrcMininumToDecode(minimumToReadBitMap, availChunksBitMap, &param, minimumToReadBitMapLen, availChunksBitMapLen);
    uint8_t targetMinimumToReadBitMap[31] = {1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
    if (memcmp(targetMinimumToReadBitMap, minimumToReadBitMap, minimumToReadBitMapLen) == 0 && ret == 0) {
        printf("get minimumToReadBitMap succ!!\r\n");
    } else {
        printf("get minimumToReadBitMap fail!!\r\n");
    }
    return 0;
}

Press Esc to exit the insert mode. Type :wq! and press Enter to save and exit the file.

Compile the test.c file into an executable file test.
1
gcc test.c -lksal -o test
Run the test executable file.
1
./test
The command output is as follows:
1
get minimumToReadBitMap succ!!

Parent topic: KSAL Development Reference