From b6fc6eccf991044d4990a5e8a3f580ec4c6b7149 Mon Sep 17 00:00:00 2001
From: Kimball Thurston <kdt3rd@gmail.com>
Date: Sun, 27 Oct 2024 06:37:23 +1300
Subject: [PATCH] Allow empty file name (#1898)

When providing a custom stream, there is no reason a filename needs to
be provided beyond clearer error messages. Because std::string does not
allow null, continue to disallow a null filename. Add a test case

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>
---
 src/lib/OpenEXRCore/context.c                |  6 +--
 src/test/OpenEXRCoreTest/read.cpp            |  2 +-
 src/test/OpenEXRTest/testExistingStreams.cpp | 56 ++++++++++++++++++++
 3 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/src/lib/OpenEXRCore/context.c b/src/lib/OpenEXRCore/context.c
index d371332f03..ae0e6a563a 100644
--- a/src/lib/OpenEXRCore/context.c
+++ b/src/lib/OpenEXRCore/context.c
@@ -150,7 +150,7 @@ exr_test_file_header (
     exr_context_t             ret   = NULL;
     exr_context_initializer_t inits = fill_context_data (ctxtdata);
 
-    if (filename && filename[0] != '\0')
+    if (filename)
     {
         rv = internal_exr_alloc_context (
             &ret,
@@ -244,7 +244,7 @@ exr_start_read (
         return EXR_ERR_INVALID_ARGUMENT;
     }
 
-    if (filename && filename[0] != '\0')
+    if (filename)
     {
         rv = internal_exr_alloc_context (
             &ret,
@@ -311,7 +311,7 @@ exr_start_write (
         return EXR_ERR_INVALID_ARGUMENT;
     }
 
-    if (filename && filename[0] != '\0')
+    if (filename)
     {
         rv = internal_exr_alloc_context (
             &ret,
diff --git a/src/test/OpenEXRCoreTest/read.cpp b/src/test/OpenEXRCoreTest/read.cpp
index f1b61ca01f..946fc40024 100644
--- a/src/test/OpenEXRCoreTest/read.cpp
+++ b/src/test/OpenEXRCoreTest/read.cpp
@@ -79,7 +79,7 @@ testReadBadArgs (const std::string& tempdir)
     EXRCORE_TEST_RVAL_FAIL (
         EXR_ERR_INVALID_ARGUMENT, exr_start_read (&f, NULL, &cinit));
     EXRCORE_TEST_RVAL_FAIL (
-        EXR_ERR_INVALID_ARGUMENT, exr_start_read (&f, "", &cinit));
+        EXR_ERR_FILE_ACCESS, exr_start_read (&f, "", &cinit));
     // windows fails on directory open, where under unix you can open
     // the directory as a file handle but not read from it
 #ifdef _WIN32
diff --git a/src/test/OpenEXRTest/testExistingStreams.cpp b/src/test/OpenEXRTest/testExistingStreams.cpp
index e9952494bc..faa8074e72 100644
--- a/src/test/OpenEXRTest/testExistingStreams.cpp
+++ b/src/test/OpenEXRTest/testExistingStreams.cpp
@@ -239,6 +239,29 @@ MMIFStream::readMemoryMapped (int n)
     return retVal;
 }
 
+class PassThruIFStream : public OPENEXR_IMF_NAMESPACE::IStream
+{
+public:
+    //-------------------------------------------------------
+    // A constructor that opens the file with the given name.
+    //-------------------------------------------------------
+
+    PassThruIFStream (MMIFStream &s) : IStream(""), _s (s) {}
+
+    virtual ~PassThruIFStream () {}
+
+    virtual bool isMemoryMapped () const { return _s.isMemoryMapped (); }
+
+    virtual bool     read (char c[/*n*/], int n) { return _s.read (c, n); }
+    virtual char*    readMemoryMapped (int n) { return _s.readMemoryMapped (n); }
+    virtual uint64_t tellg () { return _s.tellg (); }
+    virtual void     seekg (uint64_t pos) { _s.seekg (pos); }
+    virtual void     clear () { _s.clear (); }
+
+private:
+    MMIFStream &_s;
+};
+
 void
 writeReadScanLines (
     const char           fileName[],
@@ -345,6 +368,39 @@ writeReadScanLines (
         }
     }
 
+    {
+        cout << ", reading (memory-mapped, passthru)";
+        MMIFStream       ifs (fileName);
+        PassThruIFStream pfs (ifs);
+
+        RgbaInputFile in (pfs);
+
+        const Box2i& dw = in.dataWindow ();
+        int          w  = dw.max.x - dw.min.x + 1;
+        int          h  = dw.max.y - dw.min.y + 1;
+        int          dx = dw.min.x;
+        int          dy = dw.min.y;
+
+        Array2D<Rgba> p2 (h, w);
+        in.setFrameBuffer (&p2[-dy][-dx], 1, w);
+        in.readPixels (dw.min.y, dw.max.y);
+
+        if (!isLossyCompression (compression))
+        {
+            cout << ", comparing";
+            for (int y = 0; y < h; ++y)
+            {
+                for (int x = 0; x < w; ++x)
+                {
+                    assert (p2[y][x].r == p1[y][x].r);
+                    assert (p2[y][x].g == p1[y][x].g);
+                    assert (p2[y][x].b == p1[y][x].b);
+                    assert (p2[y][x].a == p1[y][x].a);
+                }
+            }
+        }
+    }
+
     cout << endl;
 
     remove (fileName);