Add raw_fd_istream. (#121)

src/support/raw_istream.cpp

@@ -7,8 +7,15 @@
 
 #include "support/raw_istream.h"
 
+#include <cstdlib>
 #include <cstring>
 
+#ifdef _WIN32
+#include <io.h>
+#else
+#include <unistd.h>
+#endif
+
 using namespace wpi;
 
 void raw_mem_istream::close() {}
@@ -22,3 +29,47 @@ void raw_mem_istream::read_impl(void* data, std::size_t len) {
   m_cur += len;
   m_left -= len;
 }
+
+raw_fd_istream::raw_fd_istream(int fd, bool shouldClose, std::size_t bufSize)
+    : m_bufSize(bufSize), m_fd(fd), m_shouldClose(shouldClose) {
+  m_cur = m_end = m_buf = static_cast<char*>(std::malloc(bufSize));
+}
+
+raw_fd_istream::~raw_fd_istream() {
+  if (m_shouldClose) close();
+  std::free(m_buf);
+}
+
+void raw_fd_istream::close() {
+  if (m_fd >= 0) {
+    ::close(m_fd);
+    m_fd = -1;
+  }
+}
+
+void raw_fd_istream::read_impl(void* data, std::size_t len) {
+  std::size_t left = m_end - m_cur;
+  if (left < len) {
+    // not enough data
+    if (m_cur == m_end) {
+#ifdef _WIN32
+      int count = ::_read(m_fd, m_buf, m_bufSize);
+#else
+      ssize_t count = ::read(m_fd, m_buf, m_bufSize);
+#endif
+      if (count < 0) {
+        error_detected();
+        return;
+      }
+      m_cur = m_buf;
+      m_end = m_buf + count;
+      return read_impl(data, len);
+    }
+
+    std::memcpy(data, m_cur, left);
+    return read_impl(static_cast<char*>(data) + left, len - left);
+  }
+
+  std::memcpy(data, m_cur, len);
+  m_cur += len;
+}