Add Arborix section directory byte readers

2026-05-07 12:28:14 -05:00
parent 1d84bf7cfa
commit a002365651
2 changed files with 177 additions and 0 deletions
--- a/lib/arborix.tri
+++ b/lib/arborix.tri
@@ -20,3 +20,58 @@ readArborixHeader = (bs :
                    (pair majorVersion
                      (pair minorVersion sectionCount))
                    afterSectionCount)))))
+
+readSectionRecord = (bs :
+  bindResult (readBytes 2 bs)
+    (sectionId afterSectionId :
+      bindResult (readBytes 4 afterSectionId)
+        (offset afterOffset :
+          bindResult (readBytes 4 afterOffset)
+            (length afterLength :
+              ok
+                (pair sectionId
+                  (pair offset length))
+                afterLength))))
+
+readSectionDirectory_ = y (self sectionCount i bs acc :
+  matchBool
+    (ok (reverse acc) bs)
+    (bindResult (readSectionRecord bs)
+      (sectionRecord afterSectionRecord :
+        self sectionCount (succ i) afterSectionRecord (pair sectionRecord acc)))
+    (equal? i sectionCount))
+
+readSectionDirectory = (sectionCount bs : readSectionDirectory_ sectionCount 0 bs t)
+
+sectionRecordId = (sectionRecord :
+  matchPair
+    (sectionId _ : sectionId)
+    sectionRecord)
+
+sectionRecordOffset = (sectionRecord :
+  matchPair
+    (_ payload :
+      matchPair
+        (offset _ : offset)
+        payload)
+    sectionRecord)
+
+sectionRecordLength = (sectionRecord :
+  matchPair
+    (_ payload :
+      matchPair
+        (_ length : length)
+        payload)
+    sectionRecord)
+
+lookupSectionRecord = y (self sectionId directory :
+  matchList
+    nothing
+    (sectionRecord rest :
+      matchBool
+        (just sectionRecord)
+        (self sectionId rest)
+        (bytesEq? sectionId (sectionRecordId sectionRecord)))
+    directory)
+
+byteSlice = (offset length bytes : bytesTake length (bytesDrop offset bytes))