From 59f3e09edfc71556208a866bb97ed9e173bd827f Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Tue, 3 May 2022 17:43:07 -0400
Subject: Make Pipeline::write take an unsigned char const* (API change)

---
 libqpdf/Pl_Flate.cc | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

(limited to 'libqpdf/Pl_Flate.cc')

diff --git a/libqpdf/Pl_Flate.cc b/libqpdf/Pl_Flate.cc
index 05a3bbcf..3ce7f434 100644
--- a/libqpdf/Pl_Flate.cc
+++ b/libqpdf/Pl_Flate.cc
@@ -84,7 +84,7 @@ Pl_Flate::warn(char const* msg, int code)
 }
 
 void
-Pl_Flate::write(unsigned char* data, size_t len)
+Pl_Flate::write(unsigned char const* data, size_t len)
 {
     if (this->m->outbuf.get() == 0) {
         throw std::logic_error(
@@ -96,7 +96,7 @@ Pl_Flate::write(unsigned char* data, size_t len)
     // Assume int is at least 32 bits.
     static size_t const max_bytes = 1 << 30;
     size_t bytes_left = len;
-    unsigned char* buf = data;
+    unsigned char const* buf = data;
     while (bytes_left > 0) {
         size_t bytes = (bytes_left >= max_bytes ? max_bytes : bytes_left);
         handleData(
@@ -109,14 +109,16 @@ Pl_Flate::write(unsigned char* data, size_t len)
 }
 
 void
-Pl_Flate::handleData(unsigned char* data, size_t len, int flush)
+Pl_Flate::handleData(unsigned char const* data, size_t len, int flush)
 {
     if (len > UINT_MAX) {
         throw std::runtime_error("Pl_Flate: zlib doesn't support data"
                                  " blocks larger than int");
     }
     z_stream& zstream = *(static_cast<z_stream*>(this->m->zdata));
-    zstream.next_in = data;
+    // zlib is known not to modify the data pointed to by next_in but
+    // doesn't declare the field value const unless compiled to do so.
+    zstream.next_in = const_cast<unsigned char*>(data);
     zstream.avail_in = QIntC::to_uint(len);
 
     if (!this->m->initialized) {
-- 
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