diff --git a/core/fdrm/fx_crypt_unittest.cpp b/core/fdrm/fx_crypt_unittest.cpp
index 4fce87e..807e68d 100644
--- a/core/fdrm/fx_crypt_unittest.cpp
+++ b/core/fdrm/fx_crypt_unittest.cpp
@@ -14,7 +14,8 @@
 namespace {
 
 std::string CRYPT_MD5String(const char* str) {
-  return GenerateMD5Base16(reinterpret_cast<const uint8_t*>(str), strlen(str));
+  return GenerateMD5Base16(
+      {reinterpret_cast<const uint8_t*>(str), strlen(str)});
 }
 
 void CheckArcFourContext(const CRYPT_rc4_context& context,
diff --git a/fpdfsdk/fpdf_annot_embeddertest.cpp b/fpdfsdk/fpdf_annot_embeddertest.cpp
index 3d5effb..6232027 100644
--- a/fpdfsdk/fpdf_annot_embeddertest.cpp
+++ b/fpdfsdk/fpdf_annot_embeddertest.cpp
@@ -1640,8 +1640,8 @@
               FPDFAnnot_GetAP(annot.get(), FPDF_ANNOT_APPEARANCEMODE_NORMAL,
                               buf.data(), normal_length_bytes));
     EXPECT_EQ(kMd5NormalAP,
-              GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()),
-                                normal_length_bytes));
+              GenerateMD5Base16({reinterpret_cast<uint8_t*>(buf.data()),
+                                 normal_length_bytes}));
 
     // Check that the string value of an AP is returned through a buffer that is
     // larger than necessary.
@@ -1650,8 +1650,8 @@
               FPDFAnnot_GetAP(annot.get(), FPDF_ANNOT_APPEARANCEMODE_NORMAL,
                               buf.data(), normal_length_bytes + 2));
     EXPECT_EQ(kMd5NormalAP,
-              GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()),
-                                normal_length_bytes));
+              GenerateMD5Base16({reinterpret_cast<uint8_t*>(buf.data()),
+                                 normal_length_bytes}));
 
     // Check that getting an AP for a mode that does not have an AP returns an
     // empty string.
@@ -1693,8 +1693,8 @@
               FPDFAnnot_GetAP(annot.get(), FPDF_ANNOT_APPEARANCEMODE_NORMAL,
                               buf.data(), normal_length_bytes));
     EXPECT_EQ(kMd5NormalAP,
-              GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()),
-                                normal_length_bytes));
+              GenerateMD5Base16({reinterpret_cast<uint8_t*>(buf.data()),
+                                 normal_length_bytes}));
   }
 
   // Save the modified document, then reopen it.
diff --git a/fpdfsdk/fpdf_attachment_embeddertest.cpp b/fpdfsdk/fpdf_attachment_embeddertest.cpp
index f1745b3..2646e21 100644
--- a/fpdfsdk/fpdf_attachment_embeddertest.cpp
+++ b/fpdfsdk/fpdf_attachment_embeddertest.cpp
@@ -9,6 +9,7 @@
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
 #include "testing/fx_string_testhelpers.h"
+#include "testing/gmock/include/gmock/gmock.h"
 #include "testing/utils/hash.h"
 
 static constexpr char kDateKey[] = "CreationDate";
@@ -42,12 +43,11 @@
 
   // Check that the content of the first attachment is correct.
   ASSERT_TRUE(FPDFAttachment_GetFile(attachment, nullptr, 0, &length_bytes));
-  std::vector<char> content_buf(length_bytes);
+  std::vector<uint8_t> content_buf(length_bytes);
   unsigned long actual_length_bytes;
   ASSERT_TRUE(FPDFAttachment_GetFile(attachment, content_buf.data(),
                                      length_bytes, &actual_length_bytes));
-  ASSERT_EQ(4u, actual_length_bytes);
-  EXPECT_EQ(std::string("test"), std::string(content_buf.data(), 4));
+  ASSERT_THAT(content_buf, testing::ElementsAre('t', 'e', 's', 't'));
 
   // Check that a non-existent key does not exist.
   EXPECT_FALSE(FPDFAttachment_HasKey(attachment, "none"));
@@ -83,8 +83,7 @@
   // Check that the calculated checksum of the file data matches expectation.
   const char kCheckSum[] = "72afcddedf554dda63c0c88e06f1ce18";
   const wchar_t kCheckSumW[] = L"<72AFCDDEDF554DDA63C0C88E06F1CE18>";
-  const std::string generated_checksum = GenerateMD5Base16(
-      reinterpret_cast<uint8_t*>(content_buf.data()), length_bytes);
+  const std::string generated_checksum = GenerateMD5Base16(content_buf);
   EXPECT_EQ(kCheckSum, generated_checksum);
 
   // Check that the stored checksum matches expectation.
diff --git a/fpdfsdk/fpdf_edit_embeddertest.cpp b/fpdfsdk/fpdf_edit_embeddertest.cpp
index 2855368..8942c28 100644
--- a/fpdfsdk/fpdf_edit_embeddertest.cpp
+++ b/fpdfsdk/fpdf_edit_embeddertest.cpp
@@ -3873,18 +3873,16 @@
 
   // Check that the raw image data has the correct length and hash value.
   unsigned long len = FPDFImageObj_GetImageDataRaw(obj, nullptr, 0);
-  std::vector<char> buf(len);
+  std::vector<uint8_t> buf(len);
   EXPECT_EQ(4091u, FPDFImageObj_GetImageDataRaw(obj, buf.data(), len));
-  EXPECT_EQ("f73802327d2e88e890f653961bcda81a",
-            GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()), len));
+  EXPECT_EQ("f73802327d2e88e890f653961bcda81a", GenerateMD5Base16(buf));
 
   // Check that the decoded image data has the correct length and hash value.
   len = FPDFImageObj_GetImageDataDecoded(obj, nullptr, 0);
   buf.clear();
   buf.resize(len);
   EXPECT_EQ(28776u, FPDFImageObj_GetImageDataDecoded(obj, buf.data(), len));
-  EXPECT_EQ(kEmbeddedImage33Checksum,
-            GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()), len));
+  EXPECT_EQ(kEmbeddedImage33Checksum, GenerateMD5Base16(buf));
 
   // Retrieve an image object with DCTDecode-encoded data stream.
   obj = FPDFPage_GetObject(page, 37);
@@ -3895,8 +3893,7 @@
   buf.clear();
   buf.resize(len);
   EXPECT_EQ(4370u, FPDFImageObj_GetImageDataRaw(obj, buf.data(), len));
-  EXPECT_EQ("6aae1f3710335023a9e12191be66b64b",
-            GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()), len));
+  EXPECT_EQ("6aae1f3710335023a9e12191be66b64b", GenerateMD5Base16(buf));
 
   // Check that the decoded image data has the correct length and hash value,
   // which should be the same as those of the raw data, since this image is
@@ -3905,8 +3902,7 @@
   buf.clear();
   buf.resize(len);
   EXPECT_EQ(4370u, FPDFImageObj_GetImageDataDecoded(obj, buf.data(), len));
-  EXPECT_EQ("6aae1f3710335023a9e12191be66b64b",
-            GenerateMD5Base16(reinterpret_cast<uint8_t*>(buf.data()), len));
+  EXPECT_EQ("6aae1f3710335023a9e12191be66b64b", GenerateMD5Base16(buf));
 
   UnloadPage(page);
 }
diff --git a/fpdfsdk/fpdf_thumbnail_embeddertest.cpp b/fpdfsdk/fpdf_thumbnail_embeddertest.cpp
index 184d4fd..789ba25 100644
--- a/fpdfsdk/fpdf_thumbnail_embeddertest.cpp
+++ b/fpdfsdk/fpdf_thumbnail_embeddertest.cpp
@@ -36,8 +36,7 @@
 
     EXPECT_EQ(kExpectedSize, FPDFPage_GetDecodedThumbnailData(
                                  page, thumb_buf.data(), length_bytes));
-    EXPECT_EQ(kHashedDecodedData,
-              GenerateMD5Base16(thumb_buf.data(), kExpectedSize));
+    EXPECT_EQ(kHashedDecodedData, GenerateMD5Base16(thumb_buf));
 
     UnloadPage(page);
   }
@@ -56,8 +55,7 @@
 
     EXPECT_EQ(kExpectedSize, FPDFPage_GetDecodedThumbnailData(
                                  page, thumb_buf.data(), length_bytes));
-    EXPECT_EQ(kHashedDecodedData,
-              GenerateMD5Base16(thumb_buf.data(), kExpectedSize));
+    EXPECT_EQ(kHashedDecodedData, GenerateMD5Base16(thumb_buf));
 
     UnloadPage(page);
   }
@@ -79,8 +77,7 @@
 
   EXPECT_EQ(kExpectedSize, FPDFPage_GetDecodedThumbnailData(
                                page, thumb_buf.data(), length_bytes));
-  EXPECT_EQ(kThumbnailWithNoFiltersChecksum,
-            GenerateMD5Base16(thumb_buf.data(), kExpectedSize));
+  EXPECT_EQ(kThumbnailWithNoFiltersChecksum, GenerateMD5Base16(thumb_buf));
 
   UnloadPage(page);
 }
@@ -116,8 +113,7 @@
 
     EXPECT_EQ(kExpectedSize, FPDFPage_GetRawThumbnailData(
                                  page, thumb_buf.data(), length_bytes));
-    EXPECT_EQ(kSimpleThumbnailChecksum,
-              GenerateMD5Base16(thumb_buf.data(), kExpectedSize));
+    EXPECT_EQ(kSimpleThumbnailChecksum, GenerateMD5Base16(thumb_buf));
 
     UnloadPage(page);
   }
@@ -135,8 +131,7 @@
 
     EXPECT_EQ(kExpectedSize, FPDFPage_GetRawThumbnailData(
                                  page, thumb_buf.data(), length_bytes));
-    EXPECT_EQ(kHashedRawData,
-              GenerateMD5Base16(thumb_buf.data(), kExpectedSize));
+    EXPECT_EQ(kHashedRawData, GenerateMD5Base16(thumb_buf));
 
     UnloadPage(page);
   }
@@ -156,8 +151,7 @@
 
   EXPECT_EQ(kExpectedSize,
             FPDFPage_GetRawThumbnailData(page, thumb_buf.data(), length_bytes));
-  EXPECT_EQ(kThumbnailWithNoFiltersChecksum,
-            GenerateMD5Base16(thumb_buf.data(), kExpectedSize));
+  EXPECT_EQ(kThumbnailWithNoFiltersChecksum, GenerateMD5Base16(thumb_buf));
 
   UnloadPage(page);
 }
@@ -269,8 +263,7 @@
 
   EXPECT_EQ(kExpectedRawSize,
             FPDFPage_GetRawThumbnailData(page, raw_thumb_buf.data(), raw_size));
-  EXPECT_EQ(kSimpleThumbnailChecksum,
-            GenerateMD5Base16(raw_thumb_buf.data(), kExpectedRawSize));
+  EXPECT_EQ(kSimpleThumbnailChecksum, GenerateMD5Base16(raw_thumb_buf));
 
   // Get the thumbnail
   ScopedFPDFBitmap thumb_bitmap(FPDFPage_GetThumbnailAsBitmap(page));
@@ -288,8 +281,7 @@
   EXPECT_EQ(kExpectedRawSize,
             FPDFPage_GetRawThumbnailData(page, new_raw_thumb_buf.data(),
                                          new_raw_size));
-  EXPECT_EQ(kSimpleThumbnailChecksum,
-            GenerateMD5Base16(new_raw_thumb_buf.data(), kExpectedRawSize));
+  EXPECT_EQ(kSimpleThumbnailChecksum, GenerateMD5Base16(new_raw_thumb_buf));
 
   UnloadPage(page);
 }
diff --git a/fpdfsdk/fpdf_view_embeddertest.cpp b/fpdfsdk/fpdf_view_embeddertest.cpp
index e015466..af732df 100644
--- a/fpdfsdk/fpdf_view_embeddertest.cpp
+++ b/fpdfsdk/fpdf_view_embeddertest.cpp
@@ -1123,9 +1123,8 @@
     EXPECT_TRUE(FPDF_GetXFAPacketContent(document(), i, data_buffer.data(),
                                          data_buffer.size(), &buflen));
     EXPECT_EQ(kExpectedResults[i].content_length, buflen);
-    EXPECT_STREQ(
-        kExpectedResults[i].content_checksum,
-        GenerateMD5Base16(data_buffer.data(), data_buffer.size()).c_str());
+    EXPECT_STREQ(kExpectedResults[i].content_checksum,
+                 GenerateMD5Base16(data_buffer).c_str());
   }
 
   // Test bad parameters.
@@ -1165,9 +1164,8 @@
   EXPECT_TRUE(FPDF_GetXFAPacketContent(document(), 0, data_buffer.data(),
                                        data_buffer.size(), &buflen));
   EXPECT_EQ(121u, buflen);
-  EXPECT_STREQ(
-      "8f912eaa1e66c9341cb3032ede71e147",
-      GenerateMD5Base16(data_buffer.data(), data_buffer.size()).c_str());
+  EXPECT_STREQ("8f912eaa1e66c9341cb3032ede71e147",
+               GenerateMD5Base16(data_buffer).c_str());
 }
 
 TEST_F(FPDFViewEmbedderTest, GetXFADataForNoForm) {
diff --git a/fxbarcode/cfx_barcode_unittest.cpp b/fxbarcode/cfx_barcode_unittest.cpp
index 3e4145b..ccf5499 100644
--- a/fxbarcode/cfx_barcode_unittest.cpp
+++ b/fxbarcode/cfx_barcode_unittest.cpp
@@ -49,8 +49,8 @@
   bool RenderDevice() { return barcode_->RenderDevice(device_.get(), matrix_); }
 
   std::string BitmapChecksum() {
-    return GenerateMD5Base16(bitmap_->GetBuffer(),
-                             bitmap_->GetPitch() * bitmap_->GetHeight());
+    return GenerateMD5Base16(
+        {bitmap_->GetBuffer(), bitmap_->GetPitch() * bitmap_->GetHeight()});
   }
 
   // Manually insert calls to this as needed for debugging.
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index 2643859..2c76808 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -308,9 +308,9 @@
   return static_cast<FPDF_FORMFILLINFO_PDFiumTest*>(form_fill_info);
 }
 
-void OutputMD5Hash(const char* file_name, const uint8_t* buffer, int len) {
+void OutputMD5Hash(const char* file_name, pdfium::span<const uint8_t> output) {
   // Get the MD5 hash and write it to stdout.
-  std::string hash = GenerateMD5Base16(buffer, len);
+  std::string hash = GenerateMD5Base16(output);
   printf("MD5:%s:%s\n", file_name, hash.c_str());
 }
 
@@ -956,7 +956,8 @@
     // file.
     if (options.md5 && !image_file_name.empty()) {
       OutputMD5Hash(image_file_name.c_str(),
-                    static_cast<const uint8_t*>(buffer), stride * height);
+                    {static_cast<const uint8_t*>(buffer),
+                     static_cast<size_t>(stride) * height});
     }
   } else {
     fprintf(stderr, "Page was too large to be rendered.\n");
diff --git a/testing/utils/hash.cpp b/testing/utils/hash.cpp
index 3170de2..71f3095 100644
--- a/testing/utils/hash.cpp
+++ b/testing/utils/hash.cpp
@@ -18,8 +18,8 @@
   return ret;
 }
 
-std::string GenerateMD5Base16(const uint8_t* data, uint32_t size) {
+std::string GenerateMD5Base16(pdfium::span<const uint8_t> data) {
   uint8_t digest[16];
-  CRYPT_MD5Generate({data, size}, digest);
+  CRYPT_MD5Generate(data, digest);
   return CryptToBase16(digest);
 }
diff --git a/testing/utils/hash.h b/testing/utils/hash.h
index 0e55165..e2a4f0a 100644
--- a/testing/utils/hash.h
+++ b/testing/utils/hash.h
@@ -7,7 +7,9 @@
 
 #include <string>
 
+#include "third_party/base/span.h"
+
 std::string CryptToBase16(const uint8_t* digest);
-std::string GenerateMD5Base16(const uint8_t* data, uint32_t size);
+std::string GenerateMD5Base16(pdfium::span<const uint8_t> data);
 
 #endif  // TESTING_UTILS_HASH_H_