readwrite.c

Apache 2.0.63 is the current stable version of the 2.0 series, and is recommended over any previous

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "win32/apr_arch_file_io.h"
#include "apr_file_io.h"
#include "apr_general.h"
#include "apr_strings.h"
#include "apr_lib.h"
#include "apr_errno.h"
#include <malloc.h>
#include "apr_arch_atime.h"
#include "apr_arch_misc.h"

/*
 * read_with_timeout() 
 * Uses async i/o to emulate unix non-blocking i/o with timeouts.
 */
static apr_status_t read_with_timeout(apr_file_t *file, void *buf, apr_size_t len, apr_size_t *nbytes)
{
    apr_status_t rv;
    *nbytes = 0;

    /* Handle the zero timeout non-blocking case */
    if (file->timeout == 0) {
        /* Peek at the pipe. If there is no data available, return APR_EAGAIN.
         * If data is available, go ahead and read it.
         */
        if (file->pipe) {
            DWORD bytes;
            if (!PeekNamedPipe(file->filehand, NULL, 0, NULL, &bytes, NULL)) {
                rv = apr_get_os_error();
                if (rv == APR_FROM_OS_ERROR(ERROR_BROKEN_PIPE)) {
                    rv = APR_EOF;
                }
                return rv;
            }
            else {
                if (bytes == 0) {
                    return APR_EAGAIN;
                }
                if (len > bytes) {
                    len = bytes;
                }
            }
        }
        else {
            /* ToDo: Handle zero timeout non-blocking file i/o 
             * This is not needed until an APR application needs to
             * timeout file i/o (which means setting file i/o non-blocking)
             */
        }
    }

    if (file->pOverlapped && !file->pipe) {
        file->pOverlapped->Offset     = (DWORD)file->filePtr;
        file->pOverlapped->OffsetHigh = (DWORD)(file->filePtr >> 32);
    }

    rv = ReadFile(file->filehand, buf, len, nbytes, file->pOverlapped);

    if (!rv) {
        rv = apr_get_os_error();
        if (rv == APR_FROM_OS_ERROR(ERROR_IO_PENDING)) {
            /* Wait for the pending i/o */
            if (file->timeout > 0) {
                /* timeout in milliseconds... */
                rv = WaitForSingleObject(file->pOverlapped->hEvent, 
                                         (DWORD)(file->timeout/1000)); 
            }
            else if (file->timeout == -1) {
                rv = WaitForSingleObject(file->pOverlapped->hEvent, INFINITE);
            }
            switch (rv) {
                case WAIT_OBJECT_0:
                    GetOverlappedResult(file->filehand, file->pOverlapped, 
                                        nbytes, TRUE);
                    rv = APR_SUCCESS;
                    break;

                case WAIT_TIMEOUT:
                    rv = APR_TIMEUP;
                    break;

                case WAIT_FAILED:
                    rv = apr_get_os_error();
                    break;

                default:
                    break;
            }

            if (rv != APR_SUCCESS) {
                if (apr_os_level >= APR_WIN_98) {
                    CancelIo(file->filehand);
                }
            }
        }
        else if (rv == APR_FROM_OS_ERROR(ERROR_BROKEN_PIPE)) {
            /* Assume ERROR_BROKEN_PIPE signals an EOF reading from a pipe */
            rv = APR_EOF;
        } else if (rv == APR_FROM_OS_ERROR(ERROR_HANDLE_EOF)) {
            /* Did we hit EOF reading from the handle? */
            rv = APR_EOF;
        }
    } else {
        /* OK and 0 bytes read ==> end of file */
        if (*nbytes == 0)
            rv = APR_EOF;
        else
            rv = APR_SUCCESS;
    }
    if (rv == APR_SUCCESS && file->pOverlapped && !file->pipe) {
        file->filePtr += *nbytes;
    }
    return rv;
}

APR_DECLARE(apr_status_t) apr_file_read(apr_file_t *thefile, void *buf, apr_size_t *len)
{
    apr_status_t rv;
    DWORD bytes_read = 0;

    if (*len <= 0) {
        *len = 0;
        return APR_SUCCESS;
    }

    /* If the file is open for xthread support, allocate and
     * initialize the overlapped and io completion event (hEvent). 
     * Threads should NOT share an apr_file_t or its hEvent.
     */
    if ((thefile->flags & APR_XTHREAD) && !thefile->pOverlapped ) {
        thefile->pOverlapped = (OVERLAPPED*) apr_pcalloc(thefile->pool, 
                                                         sizeof(OVERLAPPED));
        thefile->pOverlapped->hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
        if (!thefile->pOverlapped->hEvent) {
            rv = apr_get_os_error();
            return rv;
        }
    }

    /* Handle the ungetchar if there is one */
    if (thefile->ungetchar != -1) {
        bytes_read = 1;
        *(char *)buf = (char)thefile->ungetchar;
        buf = (char *)buf + 1;
        (*len)--;
        thefile->ungetchar = -1;
        if (*len == 0) {
            *len = bytes_read;
            return APR_SUCCESS;
        }
    }
    if (thefile->buffered) {
        char *pos = (char *)buf;
        apr_size_t blocksize;
        apr_size_t size = *len;

        apr_thread_mutex_lock(thefile->mutex);

        if (thefile->direction == 1) {
            rv = apr_file_flush(thefile);
            if (rv != APR_SUCCESS) {
                apr_thread_mutex_unlock(thefile->mutex);
                return rv;
            }
            thefile->bufpos = 0;
            thefile->direction = 0;
            thefile->dataRead = 0;
        }

        rv = 0;
        while (rv == 0 && size > 0) {
            if (thefile->bufpos >= thefile->dataRead) {
                apr_size_t read;
                rv = read_with_timeout(thefile, thefile->buffer, 
                                       APR_FILE_BUFSIZE, &read);
                if (read == 0) {
                    if (rv == APR_EOF)
                        thefile->eof_hit = TRUE;
                    break;
                }
                else {
                    thefile->dataRead = read;
                    thefile->filePtr += thefile->dataRead;
                    thefile->bufpos = 0;
                }
            }

            blocksize = size > thefile->dataRead - thefile->bufpos ? thefile->dataRead - thefile->bufpos : size;
            memcpy(pos, thefile->buffer + thefile->bufpos, blocksize);
            thefile->bufpos += blocksize;
            pos += blocksize;
            size -= blocksize;
        }

        *len = pos - (char *)buf;
        if (*len) {
            rv = APR_SUCCESS;
        }
        apr_thread_mutex_unlock(thefile->mutex);
    } else {  
        /* Unbuffered i/o */
        apr_size_t nbytes;
        rv = read_with_timeout(thefile, buf, *len, &nbytes);
        if (rv == APR_EOF)
            thefile->eof_hit = TRUE;
        *len = nbytes;
    }

    return rv;
}

APR_DECLARE(apr_status_t) apr_file_write(apr_file_t *thefile, const void *buf, apr_size_t *nbytes)
{
    apr_status_t rv;
    DWORD bwrote;

    /* If the file is open for xthread support, allocate and
     * initialize the overlapped and io completion event (hEvent). 
     * Threads should NOT share an apr_file_t or its hEvent.
     */
    if ((thefile->flags & APR_XTHREAD) && !thefile->pOverlapped ) {
        thefile->pOverlapped = (OVERLAPPED*) apr_pcalloc(thefile->pool, 
                                                         sizeof(OVERLAPPED));
        thefile->pOverlapped->hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
        if (!thefile->pOverlapped->hEvent) {
            rv = apr_get_os_error();
            return rv;
        }
    }

    if (thefile->buffered) {
        char *pos = (char *)buf;
        apr_size_t blocksize;
        apr_size_t size = *nbytes;

        apr_thread_mutex_lock(thefile->mutex);

        if (thefile->direction == 0) {
            // Position file pointer for writing at the offset we are logically reading from
            apr_off_t offset = thefile->filePtr - thefile->dataRead + thefile->bufpos;
            DWORD offlo = (DWORD)offset;
            DWORD offhi = (DWORD)(offset >> 32);
            if (offset != thefile->filePtr)
                SetFilePointer(thefile->filehand, offlo, &offhi, FILE_BEGIN);
            thefile->bufpos = thefile->dataRead = 0;
            thefile->direction = 1;
        }