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226
backend/simple_hash_demo.py
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226
backend/simple_hash_demo.py
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#!/usr/bin/env python3
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"""
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简化版文件哈希演示脚本
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"""
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import hashlib
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import requests
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import os
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# API基础URL
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BASE_URL = "http://localhost:8000/api/v1"
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USER_ID = 8
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def calculate_sha256_hash(file_content: bytes) -> str:
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"""计算文件的SHA-256哈希值"""
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return hashlib.sha256(file_content).hexdigest()
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def upload_and_demo_hash():
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"""上传文件并演示哈希功能"""
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# 创建测试文件内容
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original_content = "Hello World! 这是演示文件哈希的测试内容。"
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print("=== 文件哈希演示 ===")
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print("原始文件内容:")
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print(f"'{original_content}'")
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print(f"文件大小: {len(original_content.encode('utf-8'))} bytes")
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print()
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# 计算哈希值
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file_hash = calculate_sha256_hash(original_content.encode('utf-8'))
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print("计算的SHA-256哈希值:")
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print(file_hash)
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print()
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# 上传文件
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try:
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files = {
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"file": ("hash_demo.txt", original_content.encode('utf-8'), "text/plain")
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}
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data = {
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"user_id": USER_ID,
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"description": "哈希演示文件",
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"tags": "demo,hash",
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"is_public": "false"
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}
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response = requests.post(
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f"{BASE_URL}/files/upload",
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files=files,
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data=data
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)
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if response.status_code == 201:
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result = response.json()
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if result.get("success"):
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file_info = result["data"]["file"]
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server_hash = file_info["file_hash"]
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file_id = file_info["id"]
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print("文件上传成功!")
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print(f"文件ID: {file_id}")
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print(f"服务器哈希值: {server_hash}")
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print()
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# 验证哈希值一致性
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if file_hash == server_hash:
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print("哈希值验证通过! 客户端和服务器计算结果一致")
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else:
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print("哈希值验证失败!")
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print(f"客户端: {file_hash}")
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print(f"服务器: {server_hash}")
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return file_id, original_content, file_hash, file_info['filename']
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else:
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print(f"上传失败: {response.text}")
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return None, None, None, None
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except Exception as e:
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print(f"上传出错: {e}")
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return None, None, None, None
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def verify_download_integrity(file_id, original_content, original_hash, filename):
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"""验证下载文件的完整性"""
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print("\n=== 文件下载和完整性验证 ===")
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try:
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# 下载文件
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data = {
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"user_id": USER_ID,
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"file_id": file_id
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}
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response = requests.post(
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f"{BASE_URL}/files/download",
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json=data
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)
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if response.status_code == 200:
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downloaded_content = response.content.decode('utf-8')
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print("下载的文件内容:")
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print(f"'{downloaded_content}'")
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print()
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# 验证内容完整性
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if downloaded_content == original_content:
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print("内容完整性验证通过!")
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else:
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print("内容完整性验证失败!")
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# 计算下载文件的哈希值
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downloaded_hash = calculate_sha256_hash(downloaded_content.encode('utf-8'))
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print("下载文件的哈希值:")
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print(downloaded_hash)
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print()
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# 验证哈希值
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if downloaded_hash == original_hash:
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print("下载文件哈希验证通过! 文件完整性得到保证")
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else:
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print("下载文件哈希验证失败! 文件可能已损坏")
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print(f"原始哈希: {original_hash}")
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print(f"下载哈希: {downloaded_hash}")
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else:
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print(f"下载失败: {response.text}")
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except Exception as e:
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print(f"下载过程出错: {e}")
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def show_server_file_info(filename):
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"""显示服务器上文件的信息"""
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print("\n=== 服务器文件信息 ===")
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# 检查uploads目录
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upload_path = os.path.join("uploads", filename)
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if os.path.exists(upload_path):
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file_size = os.path.getsize(upload_path)
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print(f"文件路径: {upload_path}")
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print(f"文件大小: {file_size} bytes")
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# 计算文件哈希
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with open(upload_path, 'rb') as f:
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content = f.read()
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file_hash = calculate_sha256_hash(content)
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print(f"文件SHA-256哈希: {file_hash}")
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# 显示文件内容
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with open(upload_path, 'r', encoding='utf-8') as f:
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content = f.read()
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print(f"文件内容: '{content}'")
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else:
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print(f"文件不存在: {upload_path}")
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def demonstrate_hash_properties():
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"""演示哈希的重要特性"""
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print("\n=== 哈希特性演示 ===")
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# 特性1: 相同输入产生相同哈希
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text1 = "Hello World"
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text2 = "Hello World"
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hash1 = calculate_sha256_hash(text1.encode())
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hash2 = calculate_sha256_hash(text2.encode())
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print("特性1: 相同输入产生相同哈希")
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print(f"文本1: '{text1}' -> {hash1}")
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print(f"文本2: '{text2}' -> {hash2}")
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print(f"哈希值相同: {hash1 == hash2}")
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print()
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# 特性2: 微小变化导致完全不同的哈希
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text3 = "Hello World"
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text4 = "Hello World!" # 只多了一个感叹号
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hash3 = calculate_sha256_hash(text3.encode())
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hash4 = calculate_sha256_hash(text4.encode())
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print("特性2: 微小变化导致完全不同的哈希")
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print(f"文本3: '{text3}' -> {hash3}")
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print(f"文本4: '{text4}' -> {hash4}")
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print(f"哈希值不同: {hash3 != hash4}")
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print()
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# 特性3: 不可逆性
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sample_hash = "a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e"
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print("特性3: 哈希是单向的，无法从哈希反推原始内容")
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print(f"示例哈希: {sample_hash}")
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print("无法从这个哈希值推断出原始文本内容")
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print()
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def main():
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"""主演示函数"""
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# 演示哈希特性
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demonstrate_hash_properties()
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# 上传并演示哈希功能
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file_id, original_content, original_hash, filename = upload_and_demo_hash()
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if file_id:
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# 验证下载完整性
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verify_download_integrity(file_id, original_content, original_hash, filename)
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# 显示服务器文件信息
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show_server_file_info(filename)
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print("\n=== 总结 ===")
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print("file_hash 的作用:")
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print("1. 完整性验证 - 确保文件在传输存储过程中未损坏")
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print("2. 文件去重 - 相同内容只存储一份，节省空间")
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print("3. 安全检查 - 防止恶意文件和内容篡改")
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print("4. 快速比较 - 通过哈希值快速判断文件是否相同")
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print()
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print("如何还原文件:")
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print("1. 通过API下载: POST /api/v1/files/download")
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print("2. 直接从服务器目录读取: backend/uploads/[filename]")
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print("3. 验证文件完整性: 计算SHA-256哈希并与数据库中的file_hash比较")
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else:
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print("演示失败，无法上传测试文件")
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if __name__ == "__main__":
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main()
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