From 8c1cde4ec3f060ef0ddeff634ce7aaa645044fd6 Mon Sep 17 00:00:00 2001
From: "Chao Li(VISION)" <lchao@microsoft.com>
Date: Thu, 19 Sep 2024 12:18:26 +0000
Subject: [PATCH] Add C API qpdf_free_buffer to release memory allocated by
 stream data functions

---
 include/qpdf/qpdf-c.h |  8 ++++++++
 libqpdf/qpdf-c.cc     | 10 ++++++++++
 qpdf/qpdf-ctest.c     |  6 +++---
 qpdf/qpdf.testcov     |  1 +
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/qpdf/qpdf-c.h b/include/qpdf/qpdf-c.h
index fba952f2..d6428a20 100644
--- a/include/qpdf/qpdf-c.h
+++ b/include/qpdf/qpdf-c.h
@@ -927,6 +927,14 @@ extern "C" {
     QPDF_ERROR_CODE qpdf_oh_get_page_content_data(
         qpdf_data qpdf, qpdf_oh page_oh, unsigned char** bufp, size_t* len);
 
+    /* Call free to release the buffer allocated with malloc. This function can be used to free 
+     * buffers that were dynamically allocated by qpdf functions such as qpdf_oh_get_stream_data
+     * or qpdf_oh_get_page_content_data. The caller is responsible for calling qpdf_free_buffer
+     * to manage memory properly and avoid memory leaks.
+     */
+    QPDF_DLL
+    void qpdf_free_buffer(unsigned char** bufp);
+
     /* The data pointed to by bufp will be copied by the library. It does not need to remain valid
      * after the call returns.
      */
diff --git a/libqpdf/qpdf-c.cc b/libqpdf/qpdf-c.cc
index e2b9d821..9b04ad68 100644
--- a/libqpdf/qpdf-c.cc
+++ b/libqpdf/qpdf-c.cc
@@ -1771,6 +1771,16 @@ qpdf_oh_get_page_content_data(qpdf_data qpdf, qpdf_oh page_oh, unsigned char** b
     });
 }
 
+void
+qpdf_free_buffer(unsigned char** bufp)
+{
+    QTC::TC("qpdf", "qpdf-c called qpdf_free_buffer");
+    if (bufp && *bufp) {
+        free(*bufp);
+        *bufp = nullptr;
+    }
+}
+
 void
 qpdf_oh_replace_stream_data(
     qpdf_data qpdf,
diff --git a/qpdf/qpdf-ctest.c b/qpdf/qpdf-ctest.c
index d0c60558..69b4dcde 100644
--- a/qpdf/qpdf-ctest.c
+++ b/qpdf/qpdf-ctest.c
@@ -1151,7 +1151,7 @@ test38(char const* infile, char const* password, char const* outfile, char const
     assert(qpdf_oh_get_stream_data(qpdf, stream, qpdf_dl_none, 0, &buf, &len) == 0);
     assert(len == 53);
     assert(((int)buf[0] == 'x') && ((int)buf[1] == 0234));
-    free(buf);
+    qpdf_free_buffer(&buf);
 
     /* Test whether filterable */
     QPDF_BOOL filtered = QPDF_FALSE;
@@ -1169,8 +1169,8 @@ test38(char const* infile, char const* password, char const* outfile, char const
     assert(qpdf_oh_get_page_content_data(qpdf, page2, &buf2, &len) == 0);
     assert(len == 47);
     assert(memcmp(buf, buf2, len) == 0);
-    free(buf);
-    free(buf2);
+    qpdf_free_buffer(&buf);
+    qpdf_free_buffer(&buf2);
 
     /* errors */
     printf("page content on broken page\n");
diff --git a/qpdf/qpdf.testcov b/qpdf/qpdf.testcov
index b66ba83f..104e40bb 100644
--- a/qpdf/qpdf.testcov
+++ b/qpdf/qpdf.testcov
@@ -626,6 +626,7 @@ qpdf-c stream data filtered set 1
 qpdf-c stream data buf set 1
 qpdf-c called qpdf_oh_get_page_content_data 0
 qpdf-c called qpdf_oh_replace_stream_data 0
+qpdf-c called qpdf_free_buffer 0
 qpdf-c silence oh errors 0
 qpdf-c called qpdf_oh_get_binary_string_value 0
 qpdf-c called qpdf_oh_get_binary_utf8_value 0