Skip to content
This repository

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
tree: 1474e0d7a1
Fetching contributors…

Cannot retrieve contributors at this time

file 211 lines (174 sloc) 5.318 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211
/*
* Copyright 2006 The Android Open Source Project
*
* System utilities.
*/
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/mman.h>
#include <limits.h>
#include <errno.h>
#include <assert.h>

#define LOG_TAG "minzip"
#include "Log.h"
#include "SysUtil.h"

/*
* Having trouble finding a portable way to get this. sysconf(_SC_PAGE_SIZE)
* seems appropriate, but we don't have that on the device. Some systems
* have getpagesize(2), though the linux man page has some odd cautions.
*/
#define DEFAULT_PAGE_SIZE 4096


/*
* Create an anonymous shared memory segment large enough to hold "length"
* bytes. The actual segment may be larger because mmap() operates on
* page boundaries (usually 4K).
*/
static void* sysCreateAnonShmem(size_t length)
{
    void* ptr;

    ptr = mmap(NULL, length, PROT_READ | PROT_WRITE,
            MAP_SHARED | MAP_ANON, -1, 0);
    if (ptr == MAP_FAILED) {
        LOGW("mmap(%d, RW, SHARED|ANON) failed: %s\n", (int) length,
            strerror(errno));
        return NULL;
    }

    return ptr;
}

static int getFileStartAndLength(int fd, off_t *start_, size_t *length_)
{
    off_t start, end;
    size_t length;

    assert(start_ != NULL);
    assert(length_ != NULL);

    start = lseek(fd, 0L, SEEK_CUR);
    end = lseek(fd, 0L, SEEK_END);
    (void) lseek(fd, start, SEEK_SET);

    if (start == (off_t) -1 || end == (off_t) -1) {
        LOGE("could not determine length of file\n");
        return -1;
    }

    length = end - start;
    if (length == 0) {
        LOGE("file is empty\n");
        return -1;
    }

    *start_ = start;
    *length_ = length;

    return 0;
}

/*
* Pull the contents of a file into an new shared memory segment. We grab
* everything from fd's current offset on.
*
* We need to know the length ahead of time so we can allocate a segment
* of sufficient size.
*/
int sysLoadFileInShmem(int fd, MemMapping* pMap)
{
    off_t start;
    size_t length, actual;
    void* memPtr;

    assert(pMap != NULL);

    if (getFileStartAndLength(fd, &start, &length) < 0)
        return -1;

    memPtr = sysCreateAnonShmem(length);
    if (memPtr == NULL)
        return -1;

    actual = read(fd, memPtr, length);
    if (actual != length) {
        LOGE("only read %d of %d bytes\n", (int) actual, (int) length);
        sysReleaseShmem(pMap);
        return -1;
    }

    pMap->baseAddr = pMap->addr = memPtr;
    pMap->baseLength = pMap->length = length;

    return 0;
}

/*
* Map a file (from fd's current offset) into a shared, read-only memory
* segment. The file offset must be a multiple of the page size.
*
* On success, returns 0 and fills out "pMap". On failure, returns a nonzero
* value and does not disturb "pMap".
*/
int sysMapFileInShmem(int fd, MemMapping* pMap)
{
    off_t start;
    size_t length;
    void* memPtr;

    assert(pMap != NULL);

    if (getFileStartAndLength(fd, &start, &length) < 0)
        return -1;

    memPtr = mmap(NULL, length, PROT_READ, MAP_FILE | MAP_SHARED, fd, start);
    if (memPtr == MAP_FAILED) {
        LOGW("mmap(%d, R, FILE|SHARED, %d, %d) failed: %s\n", (int) length,
            fd, (int) start, strerror(errno));
        return -1;
    }

    pMap->baseAddr = pMap->addr = memPtr;
    pMap->baseLength = pMap->length = length;

    return 0;
}

/*
* Map part of a file (from fd's current offset) into a shared, read-only
* memory segment.
*
* On success, returns 0 and fills out "pMap". On failure, returns a nonzero
* value and does not disturb "pMap".
*/
int sysMapFileSegmentInShmem(int fd, off_t start, long length,
    MemMapping* pMap)
{
    off_t dummy;
    size_t fileLength, actualLength;
    off_t actualStart;
    int adjust;
    void* memPtr;

    assert(pMap != NULL);

    if (getFileStartAndLength(fd, &dummy, &fileLength) < 0)
        return -1;

    if (start + length > (long)fileLength) {
        LOGW("bad segment: st=%d len=%ld flen=%d\n",
            (int) start, length, (int) fileLength);
        return -1;
    }

    /* adjust to be page-aligned */
    adjust = start % DEFAULT_PAGE_SIZE;
    actualStart = start - adjust;
    actualLength = length + adjust;

    memPtr = mmap(NULL, actualLength, PROT_READ, MAP_FILE | MAP_SHARED,
                fd, actualStart);
    if (memPtr == MAP_FAILED) {
        LOGW("mmap(%d, R, FILE|SHARED, %d, %d) failed: %s\n",
            (int) actualLength, fd, (int) actualStart, strerror(errno));
        return -1;
    }

    pMap->baseAddr = memPtr;
    pMap->baseLength = actualLength;
    pMap->addr = (char*)memPtr + adjust;
    pMap->length = length;

    LOGVV("mmap seg (st=%d ln=%d): bp=%p bl=%d ad=%p ln=%d\n",
        (int) start, (int) length,
        pMap->baseAddr, (int) pMap->baseLength,
        pMap->addr, (int) pMap->length);

    return 0;
}

/*
* Release a memory mapping.
*/
void sysReleaseShmem(MemMapping* pMap)
{
    if (pMap->baseAddr == NULL && pMap->baseLength == 0)
        return;

    if (munmap(pMap->baseAddr, pMap->baseLength) < 0) {
        LOGW("munmap(%p, %d) failed: %s\n",
            pMap->baseAddr, (int)pMap->baseLength, strerror(errno));
    } else {
        LOGV("munmap(%p, %d) succeeded\n", pMap->baseAddr, pMap->baseLength);
        pMap->baseAddr = NULL;
        pMap->baseLength = 0;
    }
}
Something went wrong with that request. Please try again.