parser: Introduce per-context resource loader

SAX2.c

@@ -391,16 +391,14 @@ xmlSAX2ExternalSubset(void *ctx, const xmlChar *name,
  * @publicId: The public ID of the entity
  * @systemId: The system ID of the entity
  *
- * The entity loader, to control the loading of external entities,
- * the application can either:
- *    - override this xmlSAX2ResolveEntity() callback in the SAX block
- *    - or better use the xmlSetExternalEntityLoader() function to
- *      set up it's own entity resolution routine
+ * This is only used to load DTDs. The preferred way to install
+ * custom resolvers is xmlCtxtSetResourceLoader.
  *
- * Returns the xmlParserInputPtr if inlined or NULL for DOM behaviour.
+ * Returns a parser input.
  */
 xmlParserInputPtr
-xmlSAX2ResolveEntity(void *ctx, const xmlChar *publicId, const xmlChar *systemId)
+xmlSAX2ResolveEntity(void *ctx, const xmlChar *publicId,
+                     const xmlChar *systemId)
 {
     xmlParserCtxtPtr ctxt = (xmlParserCtxtPtr) ctx;
     xmlParserInputPtr ret = NULL;

include/libxml/parser.h

@@ -159,6 +159,10 @@ typedef struct _xmlStartTag xmlStartTag;
 typedef struct _xmlParserNsData xmlParserNsData;
 typedef struct _xmlAttrHashBucket xmlAttrHashBucket;
 
+typedef int
+(*xmlResourceLoader)(void *ctxt, const char *url, const char *publicId,
+                     int type, int flags, xmlParserInputPtr *out);
+
 /**
  * xmlParserCtxt:
  *
@@ -312,6 +316,9 @@ struct _xmlParserCtxt {
 
     xmlStructuredErrorFunc errorHandler;
     void *errorCtxt;
+
+    xmlResourceLoader resourceLoader;
+    void *resourceCtxt;
 };
 
 /**
@@ -1197,6 +1204,10 @@ XMLPUBFUN void
 		xmlSetExternalEntityLoader(xmlExternalEntityLoader f);
 XMLPUBFUN xmlExternalEntityLoader
 		xmlGetExternalEntityLoader(void);
+XMLPUBFUN void
+		xmlCtxtSetResourceLoader(xmlParserCtxtPtr ctxt,
+					 xmlResourceLoader loader,
+					 void *vctxt);
 XMLPUBFUN xmlParserInputPtr
 		xmlLoadExternalEntity	(const char *URL,
 					 const char *ID,

parserInternals.c

@@ -2306,6 +2306,8 @@ xmlDefaultExternalEntityLoader(const char *url, const char *ID,
  * @ID:  the System ID for the entity to load
  * @ctxt:  the context in which the entity is called or NULL
  *
+ * DEPRECATED: Use XML_PARSE_NONET.
+ *
  * A specific entity loader disabling network accesses, though still
  * allowing local catalog accesses for resolution.
  *
@@ -2340,7 +2342,11 @@ xmlCurrentExternalEntityLoader = xmlDefaultExternalEntityLoader;
  * xmlSetExternalEntityLoader:
  * @f:  the new entity resolver function
  *
- * Changes the defaultexternal entity resolver function for the application
+ * DEPRECATED: This is a global setting and not thread-safe. Use
+ * xmlCtxtSetResourceLoader or similar functions.
+ *
+ * Changes the default external entity resolver function for the
+ * application.
  */
 void
 xmlSetExternalEntityLoader(xmlExternalEntityLoader f) {
@@ -2350,6 +2356,8 @@ xmlSetExternalEntityLoader(xmlExternalEntityLoader f) {
 /**
  * xmlGetExternalEntityLoader:
  *
+ * DEPRECATED: See xmlSetExternalEntityLoader.
+ *
  * Get the default external entity resolver function for the application
  *
  * Returns the xmlExternalEntityLoader function pointer
@@ -2359,6 +2367,27 @@ xmlGetExternalEntityLoader(void) {
     return(xmlCurrentExternalEntityLoader);
 }
 
+/**
+ * xmlCtxtSetResourceLoader:
+ * @ctxt:  parser context
+ * @loader:  callback
+ * @vctxt:  user data
+ *
+ * Installs a custom callback to load documents, DTDs or external
+ * entities.
+ *
+ * Available since 2.14.0.
+ */
+void
+xmlCtxtSetResourceLoader(xmlParserCtxtPtr ctxt, xmlResourceLoader loader,
+                         void *vctxt) {
+    if (ctxt == NULL)
+        return;
+
+    ctxt->resourceLoader = loader;
+    ctxt->resourceCtxt = vctxt;
+}
+
 /**
  * xmlLoadExternalEntity:
  * @URL:  the URL for the entity to load
@@ -2375,6 +2404,7 @@ xmlGetExternalEntityLoader(void) {
  * The following resource loaders will be called if they were
  * registered (in order of precedence):
  *
+ * - the resource loader set with xmlCtxtSetResourceLoader
  * - the global external entity loader set with
  *   xmlSetExternalEntityLoader
  * - the per-thread xmlParserInputBufferCreateFilenameFunc set with
@@ -2397,6 +2427,22 @@ xmlLoadExternalEntity(const char *URL, const char *ID,
     if (URL == NULL)
         return(NULL);
 
+    if ((ctxt != NULL) && (ctxt->resourceLoader != NULL)) {
+        int flags = 0;
+        int code;
+
+        if ((ctxt->options & XML_PARSE_NO_UNZIP) == 0)
+            flags |= XML_INPUT_UNZIP;
+
+        code = ctxt->resourceLoader(ctxt->resourceCtxt, URL, ID, flags,
+                                    0, &ret);
+        if (code != XML_ERR_OK) {
+            xmlCtxtErrIO(ctxt, code, URL);
+            return(NULL);
+        }
+        return(ret);
+    }
+
     canonicFilename = (char *) xmlCanonicPath((const xmlChar *) URL);
     if (canonicFilename == NULL) {
         xmlCtxtErrMemory(ctxt);

xmlIO.c

@@ -2129,6 +2129,8 @@ xmlOutputBufferCreateIO(xmlOutputWriteCallback   iowrite,
  * xmlParserInputBufferCreateFilenameDefault:
  * @func: function pointer to the new ParserInputBufferCreateFilenameFunc
  *
+ * DEPRECATED: Use xmlCtxtSetResourceLoader or similar functions.
+ *
  * Registers a callback for URI input file handling
  *
  * Returns the old value of the registration function
@@ -2888,6 +2890,8 @@ xmlInitIOCallbacks(void)
  * @readFunc:  the xmlInputReadCallback
  * @closeFunc:  the xmlInputCloseCallback
  *
+ * DEPRECATED: Use xmlCtxtSetResourceLoader or similar functions.
+ *
  * Register a new set of I/O callback for handling parser input.
  *
  * Returns the registered handler number or -1 in case of error