Switch back to C implementation of sha1

Now that libnettle is built with hardware acceleration instructions

app/src/main/cpp/hash.c

@@ -0,0 +1,39 @@
+#include <unistd.h>
+
+#include <jni.h>
+#include <nettle/sha1.h>
+
+#include "ehviewer.h"
+
+#define BUFFER_SIZE 8192
+
+typedef uint8_t byte;
+
+const char hex_digits[] = "0123456789abcdef";
+
+JNIEXPORT jstring JNICALL
+Java_com_hippo_ehviewer_jni_HashKt_sha1(JNIEnv *env, jclass clazz, jint fd) {
+    EH_UNUSED(clazz);
+    struct sha1_ctx ctx;
+    sha1_init(&ctx);
+
+    size_t bytes_read;
+    byte buffer[BUFFER_SIZE];
+    while ((bytes_read = read(fd, buffer, BUFFER_SIZE)) > 0) {
+        sha1_update(&ctx, bytes_read, buffer);
+    }
+
+    byte digest[SHA1_DIGEST_SIZE];
+    sha1_digest(&ctx, SHA1_DIGEST_SIZE, digest);
+
+    byte byte;
+    char hex_digest[2 * SHA1_DIGEST_SIZE + 1];
+    for (int i = 0; i < SHA1_DIGEST_SIZE; i++) {
+        byte = digest[i];
+        hex_digest[2 * i] = hex_digits[byte >> 4 & 0xF];
+        hex_digest[2 * i + 1] = hex_digits[byte & 0xF];
+    }
+    hex_digest[2 * SHA1_DIGEST_SIZE] = '\0';
+
+    return (*env)->NewStringUTF(env, hex_digest);
+}