From 4458045c7c1ea4f17c4b2282306d2196369cc7c2 Mon Sep 17 00:00:00 2001
From: Mike Nolan <tesses@tesses.net>
Date: Sat, 13 Jun 2026 13:43:26 -0500
Subject: [PATCH] first commit

---
 CMakeLists.txt |   8 +++
 main.c         |  21 ++++++++
 mp4istrunc.h   | 133 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 162 insertions(+)
 create mode 100644 CMakeLists.txt
 create mode 100644 main.c
 create mode 100644 mp4istrunc.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..97bd212
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.16)
+
+project(mp4istrunc)
+
+add_executable(mp4istrunc main.c)
+
+install(TARGETS mp4istrunc DESTINATION bin)
+install(FILES mp4istrunc.h DESTINATION include)
\ No newline at end of file
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..be8744f
--- /dev/null
+++ b/main.c
@@ -0,0 +1,21 @@
+#define MP4ISTRUNC_IMPL
+#include "mp4istrunc.h"
+
+int main(int argc, char** argv)
+{
+    int ret=0;
+    int count = 0;
+    int i;
+    for(i = 1; i < argc; i++)
+    {
+        if(mp4trunc_istrunc(argv[i])) {
+            fprintf(stderr,"File %s was truncated\n", argv[i]);
+            ret = 1;
+            count++;
+        }
+    }
+
+    fprintf(stderr,"Files that were truncated %i\n", count);
+
+    return ret;
+}
\ No newline at end of file
diff --git a/mp4istrunc.h b/mp4istrunc.h
new file mode 100644
index 0000000..44d9ae4
--- /dev/null
+++ b/mp4istrunc.h
@@ -0,0 +1,133 @@
+#pragma once
+
+
+#if defined(__cplusplus)
+extern "C"
+#endif
+
+#if defined(MP4ISTRUNC_IMPL)
+#if defined(_WIN32) || defined(WIN32)
+
+#else
+#define _FILE_OFFSET_BITS=64
+#endif
+#endif
+
+#include <stdio.h>
+
+#define MP4TRUNC_OK 0
+#define MP4TRUNC_TRUNC 1
+
+int mp4trunc_istruncf(FILE* f);
+int mp4trunc_istrunc(const char* path);
+
+
+#if defined(MP4ISTRUNC_IMPL)
+#include <string.h>
+
+int mp4trunc_istruncf(FILE* f)
+{
+    #if defined(_WIN32) || defined(WIN32)
+
+    #if defined(MP4TRUNC_LEGACYWIN32)
+    fseek(f,0L,SEEK_END);
+    long long len = (long long)ftell(f);
+    rewind(f);
+    #else
+    _fseeki64(f,0L,SEEK_END);
+    long long len = (long long)_ftelli64(f);
+    rewind(f);
+    #endif
+    #else
+    fseeko(f,0L,SEEK_END);
+    long long len = (long long)ftello(f);
+    rewind(f);
+    #endif
+    
+
+    unsigned long long fileSizeToThisPoint = 0;
+
+    int hadWide = 0;
+
+    while(!feof(f))
+    {
+        unsigned char hdr[1024];
+        
+
+        if(fread(hdr,1,8,f) != 8) return MP4TRUNC_TRUNC;
+
+        fileSizeToThisPoint += 8;
+
+        unsigned long long atom_len = (unsigned int)hdr[0] << 24 |
+            (unsigned int)hdr[1] << 16 |
+            (unsigned int)hdr[2] << 8 |
+            (unsigned int)hdr[3];
+        
+        
+        
+        if(atom_len == 0) return MP4TRUNC_OK;
+
+
+        
+
+        if(memcmp(hdr+4,"wide",4) == 0)
+        {
+            hadWide = 1;
+            continue;
+        }
+        int isBig=0;
+
+        if(hadWide && atom_len == 1) {
+            hadWide=0;
+            isBig=1;
+            if(fread(hdr+8,1,8,f) != 8) return MP4TRUNC_TRUNC;
+            fileSizeToThisPoint+=8;
+            atom_len = (unsigned long)hdr[8] << 56 | 
+            (unsigned long long)hdr[9] << 48 |
+            (unsigned long long)hdr[10] << 40 |
+            (unsigned long long)hdr[11] << 32 |
+            (unsigned long long)hdr[12] << 24 |
+            (unsigned long long)hdr[13] << 16 |
+            (unsigned long long)hdr[14] << 8 |
+            (unsigned long long)hdr[15];
+        }
+    
+        if(memcmp(hdr+4,"mdat",4) == 0)
+        {
+            if((unsigned long long)len < (atom_len + fileSizeToThisPoint-(isBig?16:8))) return MP4TRUNC_TRUNC;
+            return MP4TRUNC_OK;
+        } else {
+            size_t left = atom_len-(isBig?16:8);
+            size_t read = 0;
+            do {
+                size_t toRead = sizeof(hdr);
+                if(left < toRead) toRead = left;
+
+                read = fread(hdr,1,toRead,f);
+
+                left -= read;
+                fileSizeToThisPoint += read;
+
+                if(feof(f) && left != 0) return MP4TRUNC_TRUNC;
+                
+            } while(read != 0);
+
+
+        }
+    }
+
+
+    return MP4TRUNC_OK;
+}
+int mp4trunc_istrunc(const char* path)
+{
+    FILE* f = fopen(path,"rb");
+    int res = mp4trunc_istruncf(f);
+    fclose(f);
+    return res;
+}
+#endif
+
+#if defined(__cplusplus)
+}
+#endif
\ No newline at end of file