sha256_blocks
sha256_blocks(&ctx->state, ctx->buf, 1);
sha256_blocks(&ctx->state, data, nblocks);
sha256_blocks(&ctx->state, ctx->buf, 1);
sha256_blocks(&ctx->state, ctx->buf, 1);
sha256_blocks(istate, derived_key.b, 1);
sha256_blocks(ostate, derived_key.b, 1);
sha256_blocks(&ctx->ostate, ctx->sha_ctx.buf, 1);
sha256_blocks(state, data, len / SHA256_BLOCK_LENGTH);
sha256_blocks(state, final_data, final_len / SHA256_BLOCK_LENGTH);