//===-- FileSystem.cpp ------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "lldb/Host/FileSystem.h"

#include "llvm/Support/MD5.h"

#include <algorithm>
#include <fstream>
#include <vector>

using namespace lldb;
using namespace lldb_private;

namespace {

bool
CalcMD5(const FileSpec &file_spec, uint64_t offset, uint64_t length, llvm::MD5::MD5Result &md5_result)
{
    llvm::MD5 md5_hash;
    std::ifstream file(file_spec.GetPath(), std::ios::binary);
    if (!file.is_open())
        return false;

    if (offset > 0)
        file.seekg(offset, file.beg);

    std::vector<char> read_buf(4096);
    uint64_t total_read_bytes = 0;
    while (!file.eof())
    {
        const uint64_t to_read = (length > 0) ?
            std::min(static_cast<uint64_t>(read_buf.size()), length - total_read_bytes) :
            read_buf.size();
        if (to_read == 0)
            break;

        file.read(&read_buf[0], to_read);
        const auto read_bytes = file.gcount();
        if (read_bytes == 0)
            break;

        md5_hash.update(llvm::StringRef(&read_buf[0], read_bytes));
        total_read_bytes += read_bytes;
    }

    md5_hash.final(md5_result);
    return true;
}

}  // namespace

bool
FileSystem::CalculateMD5(const FileSpec &file_spec, uint64_t &low, uint64_t &high)
{
    return CalculateMD5(file_spec, 0, 0, low, high);
}

bool
FileSystem::CalculateMD5(const FileSpec &file_spec,
                         uint64_t offset,
                         uint64_t length,
                         uint64_t &low,
                         uint64_t &high)
{
    llvm::MD5::MD5Result md5_result;
    if (!CalcMD5(file_spec, offset, length, md5_result))
        return false;

    const auto uint64_res = reinterpret_cast<const uint64_t*>(md5_result);
    high = uint64_res[0];
    low = uint64_res[1];

    return true;
}

bool
FileSystem::CalculateMD5AsString(const FileSpec &file_spec, std::string& digest_str)
{
    return CalculateMD5AsString(file_spec, 0, 0, digest_str);
}

bool
FileSystem::CalculateMD5AsString(const FileSpec &file_spec,
                                 uint64_t offset,
                                 uint64_t length,
                                 std::string& digest_str)
{
    llvm::MD5::MD5Result md5_result;
    if (!CalcMD5(file_spec, offset, length, md5_result))
        return false;

    llvm::SmallString<32> result_str;
    llvm::MD5::stringifyResult(md5_result, result_str);
    digest_str = result_str.c_str();
    return true;
}