split out cross reference table handling to separate module

1 files changed, 186 insertions, 0 deletions

diff --git a/src/xref.c b/src/xref.c
new file mode 100644
index 0000000..298c750
--- /dev/null
+++ b/src/xref.c
@@ -0,0 +1,186 @@
+/*
+ * Copyright 2018 Vincent Sanders <vince@netsurf-browser.org>
+ *
+ * This file is part of libnspdf.
+ *
+ * Licensed under the MIT License,
+ *                http://www.opensource.org/licenses/mit-license.php
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include <nspdf/errors.h>
+
+#include "cos_parse.h"
+#include "cos_object.h"
+#include "pdf_doc.h"
+
+
+/** indirect object */
+struct xref_table_entry {
+    /* reference identifier */
+    struct cos_reference ref;
+
+    /** offset of object */
+    uint64_t offset;
+
+    /* indirect object if already decoded */
+    struct cos_object *object;
+};
+
+static struct cos_object cos_null_obj = {
+    .type = COS_TYPE_NULL,
+};
+
+nspdferror nspdf__xref_allocate(struct nspdf_doc *doc, int64_t size)
+{
+    if (doc->xref_table != NULL) {
+        /** \todo handle freeing xref table */
+        return NSPDFERROR_SYNTAX;
+    }
+    doc->xref_table_size = size;
+
+    doc->xref_table = calloc(doc->xref_table_size,
+                             sizeof(struct xref_table_entry));
+    if (doc->xref_table == NULL) {
+        return NSPDFERROR_NOMEM;
+    }
+    return NSPDFERROR_OK;
+}
+
+nspdferror nspdf__xref_parse(struct nspdf_doc *doc, uint64_t *offset_out)
+{
+    uint64_t offset;
+    nspdferror res;
+    uint64_t objnumber; /* current object number */
+    uint64_t objcount;
+
+    offset = *offset_out;
+
+    /* xref object header */
+    if ((DOC_BYTE(doc, offset    ) != 'x') &&
+        (DOC_BYTE(doc, offset + 1) != 'r') &&
+        (DOC_BYTE(doc, offset + 2) != 'e') &&
+        (DOC_BYTE(doc, offset + 3) != 'f')) {
+        return NSPDFERROR_SYNTAX;
+    }
+    offset += 4;
+
+    res = doc_skip_ws(doc, &offset);
+    if (res != NSPDFERROR_OK) {
+        return res;
+    }
+
+    /* subsections
+     * <first object number> <number of references in subsection>
+     */
+    res = doc_read_uint(doc, &offset, &objnumber);
+    while (res == NSPDFERROR_OK) {
+        uint64_t lastobj;
+        res = doc_skip_ws(doc, &offset);
+        if (res != NSPDFERROR_OK) {
+            return res;
+        }
+
+        res = doc_read_uint(doc, &offset, &objcount);
+        if (res != NSPDFERROR_OK) {
+            return res;
+        }
+
+        res = doc_skip_ws(doc, &offset);
+        if (res != NSPDFERROR_OK) {
+            return res;
+        }
+
+        //printf("decoding subsection %lld %lld\n", objnumber, objcount);
+
+        lastobj = objnumber + objcount;
+        for (; objnumber < lastobj ; objnumber++) {
+            /* each entry is a fixed format */
+            uint64_t objindex;
+            uint64_t objgeneration;
+
+            /* object index */
+            res = doc_read_uint(doc, &offset, &objindex);
+            if (res != NSPDFERROR_OK) {
+                return res;
+            }
+            offset++; /* skip space */
+
+            res = doc_read_uint(doc, &offset, &objgeneration);
+            if (res != NSPDFERROR_OK) {
+                return res;
+            }
+            offset++; /* skip space */
+
+            if ((DOC_BYTE(doc, offset++) == 'n')) {
+                if (objnumber < doc->xref_table_size) {
+                    struct xref_table_entry *indobj;
+                    indobj = doc->xref_table + objnumber;
+
+                    indobj->ref.id = objnumber;
+                    indobj->ref.generation = objgeneration;
+                    indobj->offset = objindex;
+
+                    //printf("xref %lld %lld -> %lld\n", objnumber, objgeneration, objindex);
+                } else {
+                    //printf("index out of bounds\n");
+                }
+            }
+
+            offset += 2; /* skip EOL */
+        }
+
+        res = doc_read_uint(doc, &offset, &objnumber);
+    }
+
+    return NSPDFERROR_OK;
+}
+
+
+nspdferror
+nspdf__xref_get_referenced(struct nspdf_doc *doc, struct cos_object **cobj_out)
+{
+    nspdferror res;
+    struct cos_object *cobj;
+    struct cos_object *indirect;
+    uint64_t offset;
+    struct xref_table_entry *entry;
+
+    cobj = *cobj_out;
+
+    if (cobj->type != COS_TYPE_REFERENCE) {
+        /* not passed a reference object so just return what was passed */
+        return NSPDFERROR_OK;
+    }
+
+    entry = doc->xref_table + cobj->u.reference->id;
+
+    /* check if referenced object is in range and exists. return null object if
+     * not
+     */
+    if ((cobj->u.reference->id >= doc->xref_table_size) ||
+        (cobj->u.reference->id == 0) ||
+        (entry->ref.id == 0)) {
+        *cobj_out = &cos_null_obj;
+        return NSPDFERROR_OK;
+    }
+
+    if (entry->object == NULL) {
+        /* indirect object has never been decoded */
+        offset = entry->offset;
+        res = cos_parse_object(doc, &offset, &indirect);
+        if (res != NSPDFERROR_OK) {
+            //printf("failed to decode indirect object\n");
+            return res;
+        }
+
+        entry->object = indirect;
+    }
+
+    *cobj_out = entry->object;
+
+    return NSPDFERROR_OK;
+}