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1 files changed, 70 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/tensor/TensorTypeParser.java b/vespajlib/src/main/java/com/yahoo/tensor/TensorTypeParser.java
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+++ b/vespajlib/src/main/java/com/yahoo/tensor/TensorTypeParser.java
@@ -0,0 +1,70 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.tensor;
+
+import com.google.common.annotations.Beta;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Class for parsing a tensor type spec.
+ *
+ * @author <a href="mailto:geirst@yahoo-inc.com">Geir Storli</a>
+ */
+@Beta
+class TensorTypeParser {
+
+    private final static String START_STRING = "tensor(";
+    private final static String END_STRING = ")";
+
+    private static final Pattern indexedPattern = Pattern.compile("(\\w+)\\[(\\d*)\\]");
+    private static final Pattern mappedPattern = Pattern.compile("(\\w+)\\{\\}");
+
+    static TensorType fromSpec(String specString) {
+        if (!specString.startsWith(START_STRING) || !specString.endsWith(END_STRING)) {
+            throw new IllegalArgumentException("Tensor type spec must start with '" + START_STRING + "'" +
+                    " and end with '" + END_STRING + "', but was '" + specString + "'");
+        }
+        TensorType.Builder builder = new TensorType.Builder();
+        String dimensionsSpec = specString.substring(START_STRING.length(), specString.length() - END_STRING.length());
+        if (dimensionsSpec.isEmpty()) {
+            return builder.build();
+        }
+        for (String element : dimensionsSpec.split(",")) {
+            String trimmedElement = element.trim();
+            if (tryParseIndexedDimension(trimmedElement, builder)) {
+            } else if (tryParseMappedDimension(trimmedElement, builder)) {
+            } else {
+                throw new IllegalArgumentException("Failed parsing element '" + element +
+                        "' in type spec '" + specString + "'");
+            }
+        }
+        return builder.build();
+    }
+
+    private static boolean tryParseIndexedDimension(String element, TensorType.Builder builder) {
+        Matcher matcher = indexedPattern.matcher(element);
+        if (matcher.matches()) {
+            String dimensionName = matcher.group(1);
+            String dimensionSize = matcher.group(2);
+            if (dimensionSize.isEmpty()) {
+                builder.indexedUnbound(dimensionName);
+            } else {
+                builder.indexedBound(dimensionName, Integer.valueOf(dimensionSize));
+            }
+            return true;
+        }
+        return false;
+    }
+
+    private static boolean tryParseMappedDimension(String element, TensorType.Builder builder) {
+        Matcher matcher = mappedPattern.matcher(element);
+        if (matcher.matches()) {
+            String dimensionName = matcher.group(1);
+            builder.mapped(dimensionName);
+            return true;
+        }
+        return false;
+    }
+}
+