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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #define LOG_TAG "NativeCursorWindow"
     18 
     19 #include <jni.h>
     20 #include <fcntl.h>
     21 #include <sys/mman.h>
     22 #include <linux/ashmem.h>
     23 #include <utils/Log.h>
     24 
     25 struct Header {
     26     // Offset of the lowest unused byte in the window.
     27     uint32_t freeOffset;
     28 
     29     // Offset of the first row slot chunk.
     30     uint32_t firstChunkOffset;
     31 
     32     uint32_t numRows;
     33     uint32_t numColumns;
     34 };
     35 
     36 struct RowSlot {
     37     uint32_t offset;
     38 };
     39 
     40 #define ROW_SLOT_CHUNK_NUM_ROWS 100
     41 
     42 struct RowSlotChunk {
     43     struct RowSlot slots[ROW_SLOT_CHUNK_NUM_ROWS];
     44     uint32_t nextChunkOffset;
     45 };
     46 
     47 /* Field types. */
     48 enum {
     49     FIELD_TYPE_NULL = 0,
     50     FIELD_TYPE_INTEGER = 1,
     51     FIELD_TYPE_FLOAT = 2,
     52     FIELD_TYPE_STRING = 3,
     53     FIELD_TYPE_BLOB = 4,
     54 };
     55 
     56 /* Opaque type that describes a field slot. */
     57 struct FieldSlot {
     58     int32_t type;
     59     union {
     60         double d;
     61         int64_t l;
     62         struct {
     63             uint32_t offset;
     64             uint32_t size;
     65         } buffer;
     66     } data;
     67 } __attribute((packed));
     68 
     69 JNIEXPORT jint JNICALL
     70 Java_android_content_cts_CursorWindowContentProvider_makeNativeCursorWindowFd(JNIEnv *env, jclass clazz,
     71 jint offset, jint size, jboolean isBlob) {
     72     int fd = open("/dev/ashmem", O_RDWR);
     73     ioctl(fd, ASHMEM_SET_NAME, "Fake CursorWindow");
     74 
     75     ioctl(fd, ASHMEM_SET_SIZE, 1024);
     76 
     77     void *data = mmap(NULL, 1024, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
     78 
     79     struct Header *header = (struct Header *) data;
     80     unsigned rowSlotChunkOffset = sizeof(struct Header);
     81     struct RowSlotChunk *rowSlotChunk = (struct RowSlotChunk *)(data + rowSlotChunkOffset);
     82     unsigned fieldSlotOffset = rowSlotChunkOffset + sizeof(struct RowSlotChunk);
     83     struct FieldSlot *fieldSlot = (struct FieldSlot *) (data + fieldSlotOffset);
     84 
     85     header->numRows = 1;
     86     header->numColumns = 1;
     87     header->firstChunkOffset = rowSlotChunkOffset;
     88 
     89     rowSlotChunk->slots[0].offset = fieldSlotOffset;
     90 
     91     fieldSlot->type = isBlob ? FIELD_TYPE_BLOB : FIELD_TYPE_STRING;
     92     fieldSlot->data.buffer.offset = offset;
     93     fieldSlot->data.buffer.size = size;
     94 
     95     munmap(data, 1024);
     96 
     97     return fd;
     98 
     99 }
    100