Extract read_exactly as reusable utility function

include/osmium/io/detail/pbf_input_format.hpp

@@ -114,37 +114,14 @@ namespace osmium {
                     return size;
                 }
 
-                /**
-                 * Read exactly size bytes from fd into buffer.
-                 *
-                 * @pre Value in size parameter must fit in unsigned int
-                 * @returns true if size bytes could be read
-                 *          false if EOF was encountered
-                 */
-                bool read_exactly(char* buffer, std::size_t size) {
-                    std::size_t to_read = size;
-
-                    while (to_read > 0) {
-                        auto const read_size = osmium::io::detail::reliable_read(m_fd, buffer + (size - to_read), static_cast<unsigned int>(to_read));
-                        if (read_size == 0) { // EOF
-                            return false;
-                        }
-                        to_read -= read_size;
-                    }
-
-                    *m_offset_ptr += size;
-
-                    return true;
-                }
-
                 /**
                  * Read 4 bytes in network byte order from file. They contain
                  * the length of the following BlobHeader.
                  */
                 uint32_t read_blob_header_size_from_file() {
                     if (m_fd != -1) {
                         std::array<char, sizeof(uint32_t)> buffer{};
-                        if (!read_exactly(buffer.data(), buffer.size())) {
+                        if (!osmium::io::detail::read_exactly(m_fd, buffer.data(), static_cast<unsigned int>(buffer.size()))) {
                             return 0; // EOF
                         }
                         return check_size(get_size_in_network_byte_order(buffer.data()));
@@ -230,7 +207,7 @@ namespace osmium {
                     if (m_fd != -1) {
                         buffer.resize(size);
 
-                        if (!read_exactly(&*buffer.begin(), size)) {
+                        if (!osmium::io::detail::read_exactly(m_fd, &*buffer.begin(), static_cast<unsigned int>(size))) {
                             throw osmium::pbf_error{"unexpected EOF"};
                         }
                     } else {

include/osmium/io/detail/read_write.hpp

@@ -36,6 +36,7 @@ DEALINGS IN THE SOFTWARE.
 #include <osmium/io/writer_options.hpp>
 #include <osmium/util/file.hpp>
 
+#include <cassert>
 #include <cerrno>
 #include <cstddef>
 #include <fcntl.h>
@@ -201,6 +202,29 @@ namespace osmium {
                 return nread;
             }
 
+            /**
+             * Read exactly size bytes from fd into buffer. In contrast to reliable_read,
+             * this function will continue reading until either EOF or an error is encountered.
+             *
+             * @pre buffer Buffer for data to be read. Must be at least size bytes long.
+             * @returns true if size bytes could be read
+             *          false if EOF was encountered
+             */
+            inline bool read_exactly(int fd, char* buffer, unsigned int size) {
+                unsigned int to_read = size;
+
+                while (to_read > 0) {
+                    auto const read_size = reliable_read(fd, buffer + (size - to_read), to_read);
+                    if (read_size == 0) { // EOF
+                        return false;
+                    }
+                    assert(read_size <= to_read);
+                    to_read -= read_size;
+                }
+
+                return true;
+            }
+
             inline void reliable_fsync(const int fd) {
 #ifdef _MSC_VER
                 osmium::detail::disable_invalid_parameter_handler diph;