[C++] 使用 openssl 函式庫,計算檔案的 SHA1 值
今天用 C++ 呼叫 openssl 來計算一個檔案的 SHA1 值,
簡單用這篇記錄一下寫完的函式吧:
#include <openssl/sha.h> std::string CalcFileSHA1(const char* pFilePath) { std::string sResult = ""; if (pFilePath != NULL && *pFilePath != '\0') { FILE* pf = fopen(pFilePath, "rb"); if (pf) { // Initialize sha1 context SHA_CTX ctx = {}; int nRet = SHA1_Init(&ctx); if (nRet == SHA_FUNC_RET_SUCCESS) { char buffer[2048] = {}; size_t nBytesRead = 0; while (!feof(pf)) { // Read some bytes nBytesRead = fread(buffer, 1, sizeof(buffer), pf); if (nBytesRead == 0) { break; } // Update bytes into sha1 context if ((nRet = SHA1_Update(&ctx, buffer, nBytesRead)) != SHA_FUNC_RET_SUCCESS) { printf("Failed to update sha1 context while calculating sha1 of [%s]: nRet=%d\n", pFilePath, nRet); break; } } if (nRet == SHA_FUNC_RET_SUCCESS) { // Finalize sha1 calculation if ((nRet = SHA1_Final(reinterpret_cast<unsigned char*>(buffer), &ctx)) == SHA_FUNC_RET_SUCCESS) { snprintf(buffer+SHA_DIGEST_LENGTH, sizeof(buffer)-SHA_DIGEST_LENGTH, "%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X", static_cast<unsigned char>(buffer[0]), static_cast<unsigned char>(buffer[1]), static_cast<unsigned char>(buffer[2]), static_cast<unsigned char>(buffer[3]), static_cast<unsigned char>(buffer[4]), static_cast<unsigned char>(buffer[5]), static_cast<unsigned char>(buffer[6]), static_cast<unsigned char>(buffer[7]), static_cast<unsigned char>(buffer[8]), static_cast<unsigned char>(buffer[9]), static_cast<unsigned char>(buffer[10]), static_cast<unsigned char>(buffer[11]), static_cast<unsigned char>(buffer[12]), static_cast<unsigned char>(buffer[13]), static_cast<unsigned char>(buffer[14]), static_cast<unsigned char>(buffer[15]), static_cast<unsigned char>(buffer[16]), static_cast<unsigned char>(buffer[17]), static_cast<unsigned char>(buffer[18]), static_cast<unsigned char>(buffer[19])); sResult = buffer+SHA_DIGEST_LENGTH; } else { printf("Failed to finalize sha1 context while calculating sha1 of [%s]: nRet=%d\n", pFilePath, nRet); } } } else { printf("Failed to init sha1 context while calculating sha1 of [%s]: nRet=%d\n", pFilePath, nRet); } // Close file handle fclose(pf); } else { printf("Failed to open [%s] to calculate sha1!\n", pFilePath); } } else { printf("Invalid parameter for CalcFileSHA1: file path cannot be empty!\n"); } return sResult; }
編譯時記得要用 -lssl 來聯結 openssl 的函式庫:
libtest.so: $(OBJ_FILES) $(CC) $(CPPFLAGS) -o $@ $^ -rdynamic -shared -fPIC -lssl
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