解析libcurl在android下的移植、编译与测试

由于项目需要在ndk中使用网络开发，对于c语言网络开发来说，libcurl库是个很不错的选择，但android系统中并没有自带该库，所以就得自己移植了。
下面是移植步骤：
1.  下载curl源码
我这里下载的是curl-7.22.0，源码下载地址为：http://curl.haxx.se/download.html

2. 准备android源码编译环境，
android源码应已全部编译过，具体细节这里不详述，我这里使用的是android2.2 froyo源码树。

3.  在android中编译curl
在最新的curl源码里其实已经带有android.mk这个编译文件了，而且在这文件的开头注释部分比较详细地介绍编译方法。
1）拷贝curl源码至android源码树下的external/curl
2）cd 到 external/curl目录下，输入（红色字部分根据自己的环境做相应的更改）：

android_home=/home/braincol/workspace/android/froyo && \
ndk_home=/home/braincol/workspace/android/froyo/ndk && \
path="$android_home/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin:$path" \
./configure --host=arm-linux cc=arm-eabi-gcc --with-random=/dev/urandom \
cppflags="-i$ndk_home/platforms/android-8/arch-arm/usr/include \
-i $android_home/external/curl/include/  \
-i $android_home/external/curl/3rd/include   \
-i $android_home/external/curl   \
-i $android_home/out/target/product/generic/obj/static_libraries/libcurl_intermediates   \
-i $android_home/dalvik/libnativehelper/include/nativehelper   \
-i $android_home/system/core/include   \
-i $android_home/hardware/libhardware/include   \
-i $android_home/hardware/libhardware_legacy/include   \
-i $android_home/hardware/ril/include   \
-i $android_home/dalvik/libnativehelper/include   \
-i $android_home/frameworks/base/include   \
-i $android_home/frameworks/base/opengl/include   \
-i $android_home/frameworks/base/native/include   \
-i $android_home/external/skia/include   \
-i $android_home/out/target/product/generic/obj/include   \
-i $android_home/bionic/libc/arch-arm/include   \
-i $android_home/bionic/libc/include   \
-i $android_home/bionic/libstdc++/include   \
-i $android_home/bionic/libc/kernel/common   \
-i $android_home/bionic/libc/kernel/arch-arm   \
-i $android_home/bionic/libm/include   \
-i $android_home/bionic/libm/include/arch/arm   \
-i $android_home/bionic/libthread_db/include \
-include $android_home/system/core/include/arch/linux-arm/androidconfig.h \
-i $android_home/system/core/include/arch/linux-arm/ \
-d__arm_arch_5__ -d__arm_arch_5t__ -d__arm_arch_5e__ -d__arm_arch_5te__ -dandroid -dndebug -dndebug -dhave_config_h" \
cflags="-fno-exceptions -wno-multichar -msoft-float -fpic -ffunction-sections \
-funwind-tables -fstack-protector -wa,--noexecstack -werror=format-security \
-fno-short-enums -march=armv5te -mtune=xscale  -wno-psabi -mthumb-interwork  \
-fmessage-length=0 -w -wall -wno-unused -winit-self -wpointer-arith \
-werror=return-type -werror=non-virtual-dtor -werror=address -werror=sequence-point  \
-g -wstrict-aliasing=2 -finline-functions -fno-inline-functions-called-once \
-fgcse-after-reload -frerun-cse-after-loop -frename-registers  -udebug \
-mthumb -os -fomit-frame-pointer -fno-strict-aliasing -finline-limit=64   \
-wpointer-arith -wwrite-strings -wunused -winline -wnested-externs \
-wmissing-declarations -wmissing-prototypes -wno-long-long -wfloat-equal \
-wno-multichar -wsign-compare -wno-format-nonliteral -wendif-labels \
-wstrict-prototypes -wdeclaration-after-statement -wno-system-headers"  \
libs="-nostdlib -bdynamic -wl,-t,$android_home/build/core/armelf.x \
-wl,-dynamic-linker,/system/bin/linker -wl,--gc-sections -wl,-z,nocopyreloc \
-l$android_home/out/target/product/generic/obj/lib -wl,-z,noexecstack \
-wl,-rpath-link=$android_home/out/target/product/generic/obj/lib \
-lc -llog -lcutils -lstdc++ \
-wl,--no-undefined $android_home/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/lib/gcc/arm-eabi/4.4.0/libgcc.a  \
$android_home/out/target/product/generic/obj/lib/crtend_android.o \
-lm $android_home/out/target/product/generic/obj/lib/crtbegin_dynamic.o \
-l$android_home/external/curl/3rd/libs"

如果$android_home目录下没有ndk的开发包，那么到google的官网上下载一个放进去就行了。

3）cd 到源码根目录 mmm extern/libcurl：
编译完成之后，会生成静态库：out/target/product/generic/obj/static_libraries/libcurl_intermediates/libcurl.a  。

4）如果要生成动态库需要修改curl下的android.mk ：

local_prelink_module := false
local_module:= libcurl
local_module_tags := optional
# copy the licence to a place where android will find it.
# actually, this doesn't quite work because the build system searches
# for notice files before it gets to this point, so it will only be seen
# on subsequent builds.
all_prebuilt += $(local_path)/notice
$(local_path)/notice: $(local_path)/copying | $(acp)
$(copy-file-to-target)
#include $(build_static_library)
include $(build_shared_library)

4.  在android中测试curl
1）在android froyo源码树中下建立一个mytest目录，该目录下再建立一个curltest目录。
2）在目录curtest下创建curl-test.cpp：

#include
 "curl/curl.h"#include
 <stdio.h>;int
main() {     curl
 *curl;     curlcode
 res;     curl_global_init(curl_global_all);     curl
 = curl_easy_init();    if
(curl) {             curl_easy_setopt(curl,
 curlopt_url, "http://www.cnblogs.com/hibraincol/");
        res
 = curl_easy_perform(curl);         if
(0!=res) {                  printf("curl
 error: %d\n",
 res);                 }                 curl_easy_cleanup(curl);   
    } 
     curl_global_cleanup();    return
0;}

3）在目录curtest下创建android.mk：

#
 curl test executable#local_path
 := $(call my-dir)include
 $(clear_vars) local_c_includes
 += \    $(local_path)/3rd/include local_src_files:=
 curl-test.cpp #
 no shared libraries.local_shared_libraries
 := #
 no static libraries.local_static_libraries
 := libcurl local_module
 := curl-testinclude
 $(build_executable)

4）把libcurl的头文件拷贝到curtest目录下的3rd/include目录下：
cp -rf out/target/product/generic/obj/include/libcurl/curl  mytest/curltest/3rd/include
5）到android源码树的根目录下：mmm /mytest/curltest/

braincol@ubuntu:~/workspace/android/froyo$ mmm mytest/curltest/
============================================
platform_version_codename=rel
platform_version=2.2
target_product=generic
target_build_variant=eng
target_simulator=
target_build_type=release
target_build_apps=
target_arch=arm
host_arch=x86
host_os=linux
host_build_type=release
build_id=master
============================================
make: entering directory `/home/braincol/workspace/android/froyo'
target thumb c++: curl-test <= mytest/curltest/curl-test.cpp
mytest/curltest/curl-test.cpp:2:19: warning: extra tokens at end of #include directive
target executable: curl-test (out/target/product/generic/obj/executables/curl-test_intermediates/linked/curl-test)
target non-prelinked: curl-test (out/target/product/generic/symbols/system/bin/curl-test)
target strip: curl-test (out/target/product/generic/obj/executables/curl-test_intermediates/curl-test)
install: out/target/product/generic/system/bin/curl-test
make: leaving directory `/home/braincol/workspace/android/froyo'

可以看到在out/target/product/generic/system/bin/下生成了curl-test这个测试程序。
6）将curl-test拷贝到真机或者模拟器中运行。
  a.我这里是在android真机的根目录下建立了一个test目录.
  b.然后通过adb push将curl-test拷贝到该目录下，并更改curl-test为可执行权限：chmod 777 curl-test.
  c. adb shell 进入shell控制台，然后cd到test目录下， ./curl-test  执行，可以看到打印出的网页源码，移植成功。
 
这样在之后的android app开发中，如果需要用到libcurl的库，就可以直接out/target/product/generic/obj/include/libcurl/curl里的头文件和out/target/product/generic/obj/static_libraries/libcurl_intermediates/libcurl.a拿到app工程中去用就行了。