Include bootstrap zips as shared libraries

.gitignore

@@ -8,6 +8,7 @@ build/
 *.so
 .externalNativeBuild
 .cxx
+*.zip
 
 # Crashlytics configuations
 com_crashlytics_export_strings.xml

app/build.gradle

@@ -1,4 +1,6 @@
-apply plugin: 'com.android.application'
+plugins {
+  id "com.android.application"
+}
 
 android {
     compileSdkVersion 28
@@ -12,10 +14,21 @@ android {
 
     defaultConfig {
         applicationId "com.termux"
-        minSdkVersion 21
+        minSdkVersion 24
         targetSdkVersion 28
         versionCode 75
         versionName "0.75"
+
+        externalNativeBuild {
+            ndkBuild {
+                cFlags "-std=c11", "-Wall", "-Wextra", "-Werror", "-Os", "-fno-stack-protector", "-Wl,--gc-sections"
+            }
+        }
+
+        ndk {
+            abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
+        }
+
     }
 
     signingConfigs {
@@ -43,6 +56,12 @@ android {
         sourceCompatibility JavaVersion.VERSION_1_8
         targetCompatibility JavaVersion.VERSION_1_8
     }
+
+    externalNativeBuild {
+        ndkBuild {
+            path "src/main/cpp/Android.mk"
+        }
+    }
 }
 
 dependencies {
@@ -54,3 +73,69 @@ task versionName {
     print android.defaultConfig.versionName
   }
 }
+
+def downloadBootstrap(String arch, String expectedChecksum, int version) {
+    def digest = java.security.MessageDigest.getInstance("SHA-256")
+
+    def localUrl = "src/main/cpp/bootstrap-" + arch + ".zip"
+    def file = new File(projectDir, localUrl)
+    if (file.exists()) {
+        def buffer = new byte[8192]
+        def input = new FileInputStream(file)
+        while (true) {
+            def readBytes = input.read(buffer)
+            if (readBytes < 0) break
+            digest.update(buffer, 0, readBytes)
+        }
+        def checksum = new BigInteger(1, digest.digest()).toString(16)
+        if (checksum == expectedChecksum) {
+            return
+        } else {
+            logger.quiet("Deleting old local file with wrong hash: " + localUrl)
+            file.delete()
+        }
+    }
+
+    def remoteUrl = "https://bintray.com/termux/bootstrap/download_file?file_path=bootstrap-" + arch + "-v" + version + ".zip"
+    logger.quiet("Downloading " + remoteUrl + " ...")
+
+    file.parentFile.mkdirs()
+    def out = new BufferedOutputStream(new FileOutputStream(file))
+
+    def connection = new URL(remoteUrl).openConnection()
+    connection.setInstanceFollowRedirects(true)
+    def digestStream = new java.security.DigestInputStream(connection.inputStream, digest)
+    out << digestStream
+    out.close()
+
+    def checksum = new BigInteger(1, digest.digest()).toString(16)
+    if (checksum != expectedChecksum) {
+        file.delete()
+        throw new GradleException("Wrong checksum for " + remoteUrl + ": expected: " + expectedChecksum + ", actual: " + checksum)
+    }
+}
+
+clean {
+    doLast {
+        def tree = fileTree(new File(projectDir, 'src/main/cpp'))
+        tree.include 'bootstrap-*.zip'
+        tree.each { it.delete() }
+    }
+}
+
+task downloadBootstraps(){
+    doLast {
+        def version = 17
+        downloadBootstrap("aarch64", "1846c453e7d4399559683e9a74eb8db048d1e88872668361652752b40ea2f3a2", version)
+        downloadBootstrap("arm",     "2f5a8061a1c13d48b659cb57c3767d59f5151f247ea032e2401135701dbd8058", version)
+        downloadBootstrap("i686",    "ca0e3559c5ac925528a7c8725a83a752ca63d5c1e0ff306e5ecd6ea9dd4c1de5", version)
+        downloadBootstrap("x86_64",  "9de2ac75ed0f3370418d3c55b470c176f69180079ba9461034bc7f6195fc5872", version)
+    }
+}
+
+afterEvaluate {
+  android.applicationVariants.all { variant ->
+    variant.javaCompiler.dependsOn(downloadBootstraps)
+  }
+}
+

app/src/main/cpp/Android.mk

@@ -0,0 +1,5 @@
+LOCAL_PATH:= $(call my-dir)
+include $(CLEAR_VARS)
+LOCAL_MODULE := libtermux-bootstrap
+LOCAL_SRC_FILES := termux-bootstrap-zip.S termux-bootstrap.c
+include $(BUILD_SHARED_LIBRARY)

app/src/main/cpp/termux-bootstrap-zip.S

@@ -0,0 +1,18 @@
+     .global blob
+     .global blob_size
+     .section .rodata
+ blob:
+ #if defined __i686__
+     .incbin "bootstrap-i686.zip"
+ #elif defined __x86_64__
+     .incbin "bootstrap-x86_64.zip"
+ #elif defined __aarch64__
+     .incbin "bootstrap-aarch64.zip"
+ #elif defined __arm__
+     .incbin "bootstrap-arm.zip"
+ #else
+ # error Unsupported arch
+ #endif
+ 1:
+ blob_size:
+     .int 1b - blob

app/src/main/cpp/termux-bootstrap.c

@@ -0,0 +1,11 @@
+#include <jni.h>
+
+extern jbyte blob[];
+extern int blob_size;
+
+JNIEXPORT jbyteArray JNICALL Java_com_termux_app_TermuxInstaller_getZip(JNIEnv *env, __attribute__((__unused__)) jobject This)
+{
+    jbyteArray ret = (*env)->NewByteArray(env, blob_size);
+    (*env)->SetByteArrayRegion(env, ret, 0, blob_size, blob);
+    return ret;
+}

app/src/main/java/com/termux/app/TermuxInstaller.java

@@ -16,6 +16,7 @@ import com.termux.R;
 import com.termux.terminal.EmulatorDebug;
 
 import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -38,7 +39,7 @@ import java.util.zip.ZipInputStream;
  * <p/>
  * (3) A staging folder, $STAGING_PREFIX, is {@link #deleteFolder(File)} if left over from broken installation below.
  * <p/>
- * (4) The architecture is determined and an appropriate bootstrap zip url is determined in {@link #determineZipUrl()}.
+ * (4) The zip file is loaded from a shared library.
  * <p/>
  * (5) The zip, containing entries relative to the $PREFIX, is is downloaded and extracted by a zip input stream
  * continuously encountering zip file entries:
@@ -82,8 +83,8 @@ final class TermuxInstaller {
                     final byte[] buffer = new byte[8096];
                     final List<Pair<String, String>> symlinks = new ArrayList<>(50);
 
-                    final URL zipUrl = determineZipUrl();
-                    try (ZipInputStream zipInput = new ZipInputStream(zipUrl.openStream())) {
+                    final byte[] zipBytes = loadZipBytes();
+                    try (ZipInputStream zipInput = new ZipInputStream(new ByteArrayInputStream(zipBytes))) {
                         ZipEntry zipEntry;
                         while ((zipEntry = zipInput.getNextEntry()) != null) {
                             if (zipEntry.getName().equals("SYMLINKS.txt")) {
@@ -167,34 +168,13 @@ final class TermuxInstaller {
         }
     }
 
-    /** Get bootstrap zip url for this systems cpu architecture. */
-    private static URL determineZipUrl() throws MalformedURLException {
-        String archName = determineTermuxArchName();
-        String url = Build.VERSION.SDK_INT >= Build.VERSION_CODES.N
-            ? "https://termux.org/bootstrap-" + archName + ".zip"
-            : "https://termux.net/bootstrap/bootstrap-" + archName + ".zip";
-        return new URL(url);
+    public static byte[] loadZipBytes() {
+        // Only load the shared library when necessary to save memory usage.
+        System.loadLibrary("termux-bootstrap");
+        return getZip();
     }
 
-    private static String determineTermuxArchName() {
-        // Note that we cannot use System.getProperty("os.arch") since that may give e.g. "aarch64"
-        // while a 64-bit runtime may not be installed (like on the Samsung Galaxy S5 Neo).
-        // Instead we search through the supported abi:s on the device, see:
-        // http://developer.android.com/ndk/guides/abis.html
-        // Note that we search for abi:s in preferred order (the ordering of the
-        // Build.SUPPORTED_ABIS list) to avoid e.g. installing arm on an x86 system where arm
-        // emulation is available.
-        for (String androidArch : Build.SUPPORTED_ABIS) {
-            switch (androidArch) {
-                case "arm64-v8a": return "aarch64";
-                case "armeabi-v7a": return "arm";
-                case "x86_64": return "x86_64";
-                case "x86": return "i686";
-            }
-        }
-        throw new RuntimeException("Unable to determine arch from Build.SUPPORTED_ABIS =  " +
-            Arrays.toString(Build.SUPPORTED_ABIS));
-    }
+    public static native byte[] getZip();
 
     /** Delete a folder and all its content or throw. Don't follow symlinks. */
     static void deleteFolder(File fileOrDirectory) throws IOException {