Repo created

libs/coding/mmap_reader.cpp

@@ -0,0 +1,146 @@
+#include "coding/mmap_reader.hpp"
+
+#include "base/scope_guard.hpp"
+
+#include "std/target_os.hpp"
+
+#include <cstring>
+
+#ifdef OMIM_OS_WINDOWS
+#include "std/windows.hpp"
+#else
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#endif
+
+class MmapReader::MmapData
+{
+public:
+  explicit MmapData(std::string const & fileName, Advice advice)
+  {
+#ifdef OMIM_OS_WINDOWS
+    m_hFile = CreateFileA(fileName.c_str(), GENERIC_READ, 0, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+    if (m_hFile == INVALID_HANDLE_VALUE)
+      MYTHROW(Reader::OpenException, ("Can't open file:", fileName, "win last error:", GetLastError()));
+
+    SCOPE_GUARD(fileGuard, [this] { CloseHandle(m_hFile); });
+
+    m_hMapping = CreateFileMappingA(m_hFile, nullptr, PAGE_READONLY, 0, 0, nullptr);
+    if (!m_hMapping)
+      MYTHROW(Reader::OpenException,
+              ("Can't create file's Windows mapping:", fileName, "win last error:", GetLastError()));
+
+    SCOPE_GUARD(mappingGuard, [this] { CloseHandle(m_hMapping); });
+
+    LARGE_INTEGER fileSize;
+    if (!GetFileSizeEx(m_hFile, &fileSize))
+      MYTHROW(Reader::OpenException, ("Can't get file size:", fileName, "win last error:", GetLastError()));
+
+    m_size = fileSize.QuadPart;
+    m_memory = static_cast<uint8_t *>(MapViewOfFile(m_hMapping, FILE_MAP_READ, 0, 0, 0));
+    if (!m_memory)
+      MYTHROW(Reader::OpenException,
+              ("Can't create file's Windows mapping:", fileName, "win last error:", GetLastError()));
+
+    mappingGuard.release();
+    fileGuard.release();
+#else
+    m_fd = open(fileName.c_str(), O_RDONLY | O_NONBLOCK);
+    if (m_fd == -1)
+      MYTHROW(OpenException, ("open failed for file", fileName));
+
+    struct stat s;
+    if (-1 == fstat(m_fd, &s))
+      MYTHROW(OpenException, ("fstat failed for file", fileName));
+    m_size = s.st_size;
+
+    m_memory = static_cast<uint8_t *>(mmap(0, static_cast<size_t>(m_size), PROT_READ, MAP_PRIVATE, m_fd, 0));
+    if (m_memory == MAP_FAILED)
+    {
+      close(m_fd);
+      MYTHROW(OpenException, ("mmap failed for file", fileName));
+    }
+
+    int adv = MADV_NORMAL;
+    switch (advice)
+    {
+    case Advice::Random: adv = MADV_RANDOM; break;
+    case Advice::Sequential: adv = MADV_SEQUENTIAL; break;
+    case Advice::Normal: adv = MADV_NORMAL; break;
+    }
+
+    if (madvise(m_memory, static_cast<size_t>(s.st_size), adv) != 0)
+      LOG(LWARNING, ("madvise error:", strerror(errno)));
+#endif
+  }
+
+  ~MmapData()
+  {
+#ifdef OMIM_OS_WINDOWS
+    UnmapViewOfFile(m_memory);
+
+    CloseHandle(m_hMapping);
+    CloseHandle(m_hFile);
+#else
+    munmap(m_memory, static_cast<size_t>(m_size));
+    close(m_fd);
+#endif
+  }
+
+  uint8_t * m_memory = nullptr;
+  uint64_t m_size = 0;
+
+private:
+#ifdef OMIM_OS_WINDOWS
+  HANDLE m_hFile;
+  HANDLE m_hMapping;
+#else
+  int m_fd = 0;
+#endif
+};
+
+MmapReader::MmapReader(std::string const & fileName, Advice advice)
+  : base_type(fileName)
+  , m_data(std::make_shared<MmapData>(fileName, advice))
+  , m_offset(0)
+  , m_size(m_data->m_size)
+{}
+
+MmapReader::MmapReader(MmapReader const & reader, uint64_t offset, uint64_t size)
+  : base_type(reader.GetName())
+  , m_data(reader.m_data)
+  , m_offset(offset)
+  , m_size(size)
+{}
+
+uint64_t MmapReader::Size() const
+{
+  return m_size;
+}
+
+void MmapReader::Read(uint64_t pos, void * p, size_t size) const
+{
+  ASSERT_LESS_OR_EQUAL(pos + size, Size(), (pos, size));
+  memcpy(p, m_data->m_memory + m_offset + pos, size);
+}
+
+std::unique_ptr<Reader> MmapReader::CreateSubReader(uint64_t pos, uint64_t size) const
+{
+  ASSERT_LESS_OR_EQUAL(pos + size, Size(), (pos, size));
+  // Can't use make_unique with private constructor.
+  return std::unique_ptr<Reader>(new MmapReader(*this, m_offset + pos, size));
+}
+
+uint8_t * MmapReader::Data() const
+{
+  return m_data->m_memory;
+}
+
+void MmapReader::SetOffsetAndSize(uint64_t offset, uint64_t size)
+{
+  ASSERT_LESS_OR_EQUAL(offset + size, Size(), (offset, size));
+  m_offset = offset;
+  m_size = size;
+}