From: Antonio Valentino <antonio.valentino@tiscali.it>
Date: Tue, 19 Aug 2025 07:55:34 +0000
Subject: Fix zstd decoding

Forwarded: not-needed
Origin: https://github.com/zarr-developers/numcodecs/pull/782
---
 numcodecs/zstd.pyx | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/numcodecs/zstd.pyx b/numcodecs/zstd.pyx
index f93da63..7b88a8d 100644
--- a/numcodecs/zstd.pyx
+++ b/numcodecs/zstd.pyx
@@ -15,6 +15,9 @@ from .abc import Codec
 
 from libc.stdlib cimport malloc, realloc, free
 
+cdef extern from "stdint.h":
+    cdef size_t SIZE_MAX
+
 cdef extern from "zstd.h":
 
     unsigned ZSTD_versionNumber() nogil
@@ -202,8 +205,8 @@ def decompress(source, dest=None):
         Py_buffer* dest_pb
         char* dest_ptr
         size_t source_size, dest_size, decompressed_size
-        size_t nbytes, cbytes, blocksize
         size_t dest_nbytes
+        unsigned long long content_size
 
     # obtain source memoryview
     source_mv = ensure_continguous_memoryview(source)
@@ -214,14 +217,20 @@ def decompress(source, dest=None):
     source_size = source_pb.len
 
     try:
-
-        # determine uncompressed size
-        dest_size = ZSTD_getFrameContentSize(source_ptr, source_size)
-        if dest_size == 0 or dest_size == ZSTD_CONTENTSIZE_ERROR:
+        # determine uncompressed size using unsigned long long for full range
+        content_size = ZSTD_getFrameContentSize(source_ptr, source_size)
+        if content_size == ZSTD_CONTENTSIZE_UNKNOWN and dest is None:
+            return stream_decompress(source_pb)
+        elif content_size == ZSTD_CONTENTSIZE_UNKNOWN:
+            # dest is not None
+            # set dest_size based on dest
+            pass
+        elif content_size == ZSTD_CONTENTSIZE_ERROR or content_size == 0:
             raise RuntimeError('Zstd decompression error: invalid input data')
+        elif content_size > (<unsigned long long>SIZE_MAX):
+            raise RuntimeError('Zstd decompression error: content size too large for platform')
 
-        if dest_size == ZSTD_CONTENTSIZE_UNKNOWN and dest is None:
-            return stream_decompress(source_pb)
+        dest_size = <size_t>content_size
 
         # setup destination buffer
         if dest is None:
@@ -236,7 +245,7 @@ def decompress(source, dest=None):
         dest_ptr = <char*>dest_pb.buf
         dest_nbytes = dest_pb.len
 
-        if dest_size == ZSTD_CONTENTSIZE_UNKNOWN:
+        if content_size == ZSTD_CONTENTSIZE_UNKNOWN:
             dest_size = dest_nbytes
 
         # validate output buffer