c语言sha256算法代码

以下是一个简单的C语言SHA-256算法的实现代码：

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

#define ROT_RIGHT(x, n) (((x) >> (n)) | ((x) << (32 - (n))))

#define SHA256_BLOCK_SIZE 64
#define SHA256_DIGEST_SIZE 32

typedef struct {
    uint32_t total[2];
    uint32_t state[8];
    uint8_t buffer[SHA256_BLOCK_SIZE];
} sha256_ctx;

static const uint32_t k[64] = {
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

static void sha256_transform(sha256_ctx *ctx, const uint8_t *data) {
    uint32_t a, b, c, d, e, f, g, h, t1, t2, m[64];
    uint32_t i;

    for (i = 0; i < 16; i++) {
        m[i] = ((uint32_t)data[i * 4] << 24) | ((uint32_t)data[i * 4 + 1] << 16) |
               ((uint32_t)data[i * 4 + 2] << 8) | ((uint32_t)data[i * 4 + 3]);
    }

    for (i = 16; i < 64; i++) {
        m[i] = m[i - 16] + ROT_RIGHT(m[i - 15], 7) +
               m[i - 7] + ROT_RIGHT(m[i - 2], 17);
    }

    a = ctx->state[0];
    b = ctx->state[1];
    c = ctx->state[2];
    d = ctx->state[3];
    e = ctx->state[4];
    f = ctx->state[5];
    g = ctx->state[6];
    h = ctx->state[7];

    for (i = 0; i < 64; i++) {
        t1 = h + ROT_RIGHT(e, 6) + ((e & f) ^ (~e & g)) + k[i] + m[i];
        t2 = ROT_RIGHT(a, 2) + ((a & b) ^ (a & c) ^ (b & c));
        h = g;
        g = f;
        f = e;
        e = d + t1;
        d = c;
        c = b;
        b = a;
        a = t1 + t2;
    }

    ctx->state[0] += a;
    ctx->state[1] += b;
    ctx->state[2] += c;
    ctx->state[3] += d;
    ctx->state[4] += e;
    ctx->state[5] += f;
    ctx->state[6] += g;
    ctx->state[7] += h;
}

static void sha256_init(sha256_ctx *ctx) {
    memset(ctx, 0, sizeof(sha256_ctx));

    ctx->state[0] = 0x6a09e667;
    ctx->state[1] = 0xbb67ae85;
    ctx->state[2] = 0x3c6ef372;
    ctx->state[3] = 0xa54ff53a;
    ctx->state[4] = 0x510e527f;
    ctx->state[5] = 0x9b05688c;
    ctx->state[6] = 0x1f83d9ab;
    ctx->state[7] = 0x5be0cd19;
}

static void sha256_update(sha256_ctx *ctx, const uint8_t *data, size_t len) {
    size_t i, j;

    for (i = 0; i < len; i++) {
        j = (ctx->total[0] >> 3) & (SHA256_BLOCK_SIZE - 1);
        ctx->buffer[j++] = data[i];
        ctx->total[0] += 8;

        if (j == SHA256_BLOCK_SIZE) {
            sha256_transform(ctx, ctx->buffer);
            ctx->total[1]++;
            j = 0;
        }
    }
}

static void sha256_final(sha256_ctx *ctx, uint8_t *digest) {
    uint8_t i, j;

    i = (ctx->total[0] >> 3) & (SHA256_BLOCK_SIZE - 1);
    ctx->buffer[i++] = 0x80;

    if (i > 56) {
        memset(&ctx->buffer[i], 0, SHA256_BLOCK_SIZE - i);
        sha256_transform(ctx, ctx->buffer);
        memset(ctx->buffer, 0, 56);
    } else {
        memset(&ctx->buffer[i], 0, 56 - i);
    }

    ctx->total[0] *= 8;
    ctx->buffer[63] = (ctx->total[0] >> 0) & 0xff;
    ctx->buffer[62] = (ctx->total[0] >> 8) & 0xff;
    ctx->buffer[61] = (ctx->total[0] >> 16) & 0xff;
    ctx->buffer[60] = (ctx->total[0] >> 24) & 0xff;
    ctx->buffer[59] = (ctx->total[1] >> 0) & 0xff;
    ctx->buffer[58] = (ctx->total[1] >> 8) & 0xff;
    ctx->buffer[57] = (ctx->total[1] >> 16) & 0xff;
    ctx->buffer[56] = (ctx->total[1] >> 24) & 0xff;
    sha256_transform(ctx, ctx->buffer);

    for (i = 0, j = 0; i < 8; i++, j += 4) {
        digest[j] = (ctx->state[i] >> 24) & 0xff;
        digest[j + 1] = (ctx->state[i] >> 16) & 0xff;
        digest[j + 2] = (ctx->state[i] >> 8) & 0xff;
        digest[j + 3] = ctx->state[i] & 0xff;
    }
}

void sha256(const uint8_t *data, size_t len, uint8_t *digest) {
    sha256_ctx ctx;

    sha256_init(&ctx);
    sha256_update(&ctx, data, len);
    sha256_final(&ctx, digest);
}

这个实现仅供参考，实际生产环境中建议使用经过严格测试和验证的现有库或工具。