4 files changed, 94 insertions, 0 deletions
diff --git a/src/main/java/com/keuin/psmb4j/util/InputStreamUtils.java b/src/main/java/com/keuin/psmb4j/util/InputStreamUtils.java
new file mode 100644
index 0000000..7b3fd9c
--- /dev/null
+++ b/src/main/java/com/keuin/psmb4j/util/InputStreamUtils.java
@@ -0,0 +1,56 @@
+package com.keuin.psmb4j.util;
+
+import com.keuin.psmb4j.util.error.SocketClosedException;
+import com.keuin.psmb4j.util.error.StringLengthExceededException;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public class InputStreamUtils {
+    /**
+     * Read until '\0', the trailing '\0' is dropped.
+     */
+    public static String readCString(InputStream stream) throws IOException {
+        var sb = new StringBuilder();
+        int c;
+        while ((c = stream.read()) > 0) {
+            sb.append((char) c);
+        }
+        return sb.toString();
+    }
+
+    /**
+     * Read a C style string, with a length limit.
+     * If the string is longer than given limit,
+     * a {@link StringLengthExceededException} will be thrown.
+     */
+    public static String readCString(InputStream stream, long maxLength) throws IOException {
+        var sb = new StringBuilder();
+        int c;
+        long length = 0;
+        while ((c = stream.read()) > 0) {
+            sb.append((char) c);
+            if (++length > maxLength) {
+                throw new StringLengthExceededException(maxLength);
+            }
+        }
+        return sb.toString();
+    }
+
+    /**
+     * Read fixed length bytes from stream.
+     * If not enough, a {@link SocketClosedException} will be thrown.
+     */
+    public static byte[] readBytes(InputStream stream, int length) throws IOException {
+        var buffer = new byte[length];
+        int c;
+        for (int i = 0; i < length; i++) {
+            if ((c = stream.read()) >= 0) {
+                buffer[i] = (byte) c;
+            } else {
+                throw new SocketClosedException(length, i);
+            }
+        }
+        return buffer;
+    }
+}
diff --git a/src/main/java/com/keuin/psmb4j/util/StringUtils.java b/src/main/java/com/keuin/psmb4j/util/StringUtils.java
new file mode 100644
index 0000000..036a560
--- /dev/null
+++ b/src/main/java/com/keuin/psmb4j/util/StringUtils.java
@@ -0,0 +1,14 @@
+package com.keuin.psmb4j.util;
+
+import java.nio.charset.StandardCharsets;
+
+public class StringUtils {
+    /**
+     * If the string can be encoded into binary using ASCII.
+     */
+    @SuppressWarnings("BooleanMethodIsAlwaysInverted")
+    public static boolean isPureAscii(String v) {
+        return StandardCharsets.US_ASCII.newEncoder().canEncode(v);
+        // or "ISO-8859-1" for ISO Latin 1
+    }
+}
diff --git a/src/main/java/com/keuin/psmb4j/util/error/SocketClosedException.java b/src/main/java/com/keuin/psmb4j/util/error/SocketClosedException.java
new file mode 100644
index 0000000..e7c9b2d
--- /dev/null
+++ b/src/main/java/com/keuin/psmb4j/util/error/SocketClosedException.java
@@ -0,0 +1,15 @@
+package com.keuin.psmb4j.util.error;
+
+import java.io.IOException;
+
+/**
+ * The socket closed before enough bytes have been read out.
+ */
+public class SocketClosedException extends IOException {
+    public SocketClosedException() {
+    }
+
+    public SocketClosedException(long expected, long actual) {
+        super(String.format("expected %d bytes, EOF after reading %d bytes", expected, actual));
+    }
+}
diff --git a/src/main/java/com/keuin/psmb4j/util/error/StringLengthExceededException.java b/src/main/java/com/keuin/psmb4j/util/error/StringLengthExceededException.java
new file mode 100644
index 0000000..afb08b6
--- /dev/null
+++ b/src/main/java/com/keuin/psmb4j/util/error/StringLengthExceededException.java
@@ -0,0 +1,9 @@
+package com.keuin.psmb4j.util.error;
+
+import java.io.IOException;
+
+public class StringLengthExceededException extends IOException {
+    public StringLengthExceededException(long length) {
+        super(String.format("String is too long (%d Bytes)", length));
+    }
+}