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+# PicoSHA2 - a C++ SHA256 hash generator
+
+Copyright © 2017 okdshin
+
+## Introduction
+
+PicoSHA2 is a tiny SHA256 hash generator for C++ with following properties:
+
+- header-file only
+- no external dependencies (only uses standard C++ libraries)
+- STL-friendly
+- licensed under MIT License
+
+## Generating SHA256 hash and hash hex string
+
+```c++
+// any STL sequantial container (vector, list, dequeue...)
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+
+std::vector<unsigned char> hash(picosha2::k_digest_size);
+picosha2::hash256(src_str.begin(), src_str.end(), hash.begin(), hash.end());
+
+std::string hex_str = picosha2::bytes_to_hex_string(hash.begin(), hash.end());
+```
+
+## Generating SHA256 hash and hash hex string from byte stream
+
+```c++
+picosha2::hash256_one_by_one hasher;
+...
+hasher.process(block.begin(), block.end());
+...
+hasher.finish();
+
+std::vector<unsigned char> hash(picosha2::k_digest_size);
+hasher.get_hash_bytes(hash.begin(), hash.end());
+
+std::string hex_str = picosha2::get_hash_hex_string(hasher);
+```
+
+The file `example/interactive_hasher.cpp` has more detailed information.
+
+## Generating SHA256 hash from a binary file
+
+```c++
+std::ifstream f("file.txt", std::ios::binary);
+std::vector<unsigned char> s(picosha2::k_digest_size);
+picosha2::hash256(f, s.begin(), s.end());
+```
+
+This `hash256` may use less memory than reading whole of the file.
+
+## Generating SHA256 hash hex string from std::string
+
+```c++
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+std::string hash_hex_str;
+picosha2::hash256_hex_string(src_str, hash_hex_str);
+std::cout << hash_hex_str << std::endl;
+//this output is "d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592"
+```
+
+```c++
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+std::string hash_hex_str = picosha2::hash256_hex_string(src_str);
+std::cout << hash_hex_str << std::endl;
+//this output is "d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592"
+```
+
+```c++
+std::string src_str = "The quick brown fox jumps over the lazy dog.";//add '.'
+std::string hash_hex_str = picosha2::hash256_hex_string(src_str.begin(), src_str.end());
+std::cout << hash_hex_str << std::endl;
+//this output is "ef537f25c895bfa782526529a9b63d97aa631564d5d789c2b765448c8635fb6c"
+```
+
+## Generating SHA256 hash hex string from byte sequence
+
+```c++
+std::vector<unsigned char> src_vect(...);
+std::string hash_hex_str;
+picosha2::hash256_hex_string(src_vect, hash_hex_str);
+```
+
+```c++
+std::vector<unsigned char> src_vect(...);
+std::string hash_hex_str = picosha2::hash256_hex_string(src_vect);
+```
+
+```c++
+unsigned char src_c_array[picosha2::k_digest_size] = {...};
+std::string hash_hex_str;
+picosha2::hash256_hex_string(src_c_array, src_c_array+picosha2::k_digest_size, hash_hex_str);
+```
+
+```c++
+unsigned char src_c_array[picosha2::k_digest_size] = {...};
+std::string hash_hex_str = picosha2::hash256_hex_string(src_c_array, src_c_array+picosha2::k_digest_size);
+```
+
+
+## Generating SHA256 hash byte sequence from STL sequential container
+
+```c++
+//any STL sequantial container (vector, list, dequeue...)
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+
+//any STL sequantial containers (vector, list, dequeue...)
+std::vector<unsigned char> hash(picosha2::k_digest_size);
+
+// in: container, out: container
+picosha2::hash256(src_str, hash);
+```
+
+```c++
+//any STL sequantial container (vector, list, dequeue...)
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+
+//any STL sequantial containers (vector, list, dequeue...)
+std::vector<unsigned char> hash(picosha2::k_digest_size);
+
+// in: iterator pair, out: contaner
+picosha2::hash256(src_str.begin(), src_str.end(), hash);
+```
+
+```c++
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+unsigned char hash_byte_c_array[picosha2::k_digest_size];
+// in: container, out: iterator(pointer) pair
+picosha2::hash256(src_str, hash_byte_c_array, hash_byte_c_array+picosha2::k_digest_size);
+```
+
+```c++
+std::string src_str = "The quick brown fox jumps over the lazy dog";
+std::vector<unsigned char> hash(picosha2::k_digest_size);
+// in: iterator pair, out: iterator pair
+picosha2::hash256(src_str.begin(), src_str.end(), hash.begin(), hash.end());
+```