implemented basic char_to_java()

readme.md

@@ -125,6 +125,9 @@ You can run `$INSTALL_DIR/bin/native-platform` to run the test application.
 
 ### Improvements
 
+* Cache class, method and field lookups (in particular for String conversions).
+* Determine C charset once at startup
+* Change readLink() implementation so that it does not need to NULL terminate the encoded content
 * Implement java_to_char_str()
 * Use iconv() to convert from C char string to UTF-16 when converting from C char string to Java String.
 * Support for cygwin terminal

src/main/cpp/posix.cpp

@@ -23,11 +23,26 @@ void mark_failed_with_errno(JNIEnv *env, const char* message, jobject result) {
     mark_failed_with_code(env, message, errno, result);
 }
 
-char_str* java_to_char_str(JNIEnv *env, jstring string, jobject result) {
+char* java_to_char(JNIEnv *env, jstring string, jobject result) {
-    return NULL;
+    // TODO - share this code with nnn_getSystemInfo() below
-}
+    locale_t locale = newlocale(LC_CTYPE_MASK, "", NULL);
+    if (locale == NULL) {
+        mark_failed_with_message(env, "could not create locale", result);
+        return NULL;
+    }
 
-void char_str_free(char_str* str) {
+    jstring encoding = env->NewStringUTF(nl_langinfo_l(CODESET, locale));
+    freelocale(locale);
+
+    jclass strClass = env->FindClass("java/lang/String");
+    jmethodID method = env->GetMethodID(strClass, "getBytes", "(Ljava/lang/String;)[B");
+    jbyteArray byteArray = (jbyteArray)env->CallObjectMethod(string, method, encoding);
+    size_t len = env->GetArrayLength(byteArray);
+    char* chars = (char*)malloc(len + 1);
+    env->GetByteArrayRegion(byteArray, 0, len, (jbyte*)chars);
+    chars[len] = 0;
+
+    return chars;
 }
 
 jstring char_to_java(JNIEnv* env, const char* chars, jobject result) {

src/main/headers/generic.h

@@ -51,26 +51,12 @@ extern void wchar_str_free(wchar_str* str);
  */
 extern jstring wchar_to_java(JNIEnv* env, const wchar_t* chars, size_t len, jobject result);
 
-typedef struct char_struct {
-    // NULL terminated
-    char* chars;
-    // Number of chars in the string, excluding the NULL terminator
-    size_t len;
-    jstring source;
-    JNIEnv *env;
-} char_str;
-
 /*
- * Converts the given Java string to a char_str. Should call char_str_free() when finished.
+ * Converts the given Java string to a char_str. Should call free() when finished.
  *
  * Returns NULL on failure.
  */
-extern char_str* java_to_char_str(JNIEnv *env, jstring string, jobject result);
+extern char* java_to_char(JNIEnv *env, jstring string, jobject result);
-
-/*
- * Releases resources used by the given string.
- */
-extern void char_str_free(char_str* str);
 
 /*
  * Converts the given NULL terminated char string to a Java string.