From: Ralph Ronnquist <rrq@rrq.au>
Date: Wed, 27 Aug 2025 10:25:00 +0000 (+1000)
Subject: Allow exact-match excludes in PATHMAPNOT
X-Git-Url: https://git.rrq.selfhost.au/?a=commitdiff_plain;h=65f5db1b5f6b9716a6e3bdd7d8f9dd9275fd8af8;p=rrq%2Fpathmap.git

Allow exact-match excludes in PATHMAPNOT
---

diff --git a/libpathmap-0.c b/libpathmap-0.c
index b327bb9..f7dea49 100644
--- a/libpathmap-0.c
+++ b/libpathmap-0.c
@@ -36,6 +36,7 @@ static struct {
     int count;
     int root_length;
     char *root;
+    int root_index;
 } prefix;
 
 // Alphabetical ordering of char* records.
@@ -44,6 +45,61 @@ static int alphorder(const void *a, const void *b) {
     return x;
 }
 
+// Binary search for a given path prefix.
+static int binsearch(const char *path) {
+    int lo = 0;
+    int hi = prefix.count;
+    while ( lo < hi ) {
+	int m = ( lo + hi ) / 2;
+	int x = strcmp( path, prefix.data[ m ] );
+	if ( x == 0 ) {
+	    return m;
+	}
+	if ( x < 0 ) {
+	    hi = m;
+	} else {
+	    lo = m + 1;
+	}
+    }
+    return - lo - 1;
+}
+
+// Use binary search for a given path prefix, and for mismatch check
+// if entry prior to insertion is a path prefix. Returns the index of
+// longest path prefix match or (-i-1)<0 for mismatch (indicating
+// insertion point i)
+static int prefixsearch(const char *path) {
+    int lo = binsearch( path );
+#if 0
+    if ( lo >= 0 ) {
+	fprintf( stderr, "libpathmap:  [%d] %s\n", lo, prefix.data[ lo ] );
+    } else {
+	fprintf( stderr, "libpathmap:  [%d] ... \n", lo );
+    }
+#endif
+    if ( lo >= -1 ) {
+	return lo;
+    }
+    int p = - lo - 2;
+    // p = before insertion point for mismatch; check if it's prefix
+    int n = strlen( prefix.data[ p ] );
+    if ( ( strncmp( prefix.data[ p ], path, n ) != 0 ) ) {
+	return lo; // Not a prefix
+    }
+    if ( *(path+n) == '/' ) {
+	//fprintf( stderr, "libpathmap:  exclude prefix %s\n",
+	//	 prefix.data[ p ] );
+	return p; // matching prefix at p
+    }
+    // The root path must be prefix; any exclude path may match in full
+    if ( ( p != prefix.root_index ) && *(path+n) == 0 ) {
+	//fprintf( stderr, "libpathmap:  exclude match %s\n",
+	//	 prefix.data[ p ] );
+	return p;
+    }
+    return lo;
+}
+
 // Utility function to load the prefixes.
 static void load_prefixes() {
     char *data = getenv( PATHMAPNOT );
@@ -75,34 +131,7 @@ static void load_prefixes() {
     prefix.root = prefix.data[ 0 ];
     prefix.root_length = strlen( prefix.root );
     qsort( prefix.data, n, sizeof( char* ), alphorder );
-}
-
-// Binary search for a given path prefix. Returns the index of longest
-// prefix match or (-i-1)<0 for mismatch (indicating insertion point i)
-static int binsearch(const char *path) {
-    int lo = 0;
-    int hi = prefix.count;
-    while ( lo < hi ) {
-	int m = ( lo + hi ) / 2;
-	int x = strcmp( path, prefix.data[ m ] );
-	if ( x == 0 ) {
-	    return m;
-	}
-	if ( x < 0 ) {
-	    hi = m;
-	} else {
-	    lo = m + 1;
-	}
-    }
-    // lo = insertion point for mismatch; check if lo-1 is prefix
-    if ( lo > 0 ) {
-	int n = strlen( prefix.data[ lo - 1 ] );
-	if ( ( strncmp( prefix.data[ lo - 1 ], path, n ) == 0 ) &&
-	     ( *(path+n) == '/' ) ) {
-	    return lo - 1;
-	}
-    }
-    return - lo - 1;
+    prefix.root_index = binsearch( prefix.root );
 }
 
 // Utility function to lookup a matching prefix for the given path. If
@@ -111,16 +140,18 @@ static int binsearch(const char *path) {
 // by the given path. Note that prefixing only applies to absolute
 // paths.
 static char *maybe_add_prefix(const char *path) {
-    fprintf( stderr, "libpathmap: check %s\n", path );
     if ( prefix.count > 0 && *path == '/' ) {
-	int x = binsearch( path );
+	//fprintf( stderr, "libpathmap: check %s\n", path );
+	int x = prefixsearch( path );
 	//fprintf( stderr, "libpathmap: %d %s\n", x, path );
 	if ( x < 0 ) {
 	    char *p = (char*)malloc( strlen( path ) + prefix.root_length + 1 );
 	    memcpy( p, prefix.root, prefix.root_length );
 	    strcpy( p + prefix.root_length, path );
-	    fprintf( stderr, "libpathmap: => %s\n", p );
+	    //fprintf( stderr, "libpathmap: [%s] %s\n", prefix.root, path );
 	    return p;
+	} else {
+	    //fprintf( stderr, "libpathmap: [] %s\n", path );
 	}
     }
     return 0;
diff --git a/libtarmap-0.c b/libtarmap-0.c
index 8625616..385bfae 100644
--- a/libtarmap-0.c
+++ b/libtarmap-0.c
@@ -135,9 +135,9 @@ void so_init() {
     }
     //fprintf( stderr, "libtarmap: %s\n", tarfile? tarfile : "(null)" );
     libc6 = dlopen( "libc.so.6", RTLD_LAZY );
-    real_openat = dlsym( libc6, "openat" );
-    real_open = dlsym( libc6, "open" );
-    real_fopen = dlsym( libc6, "fopen" );
+    //real_openat = dlsym( libc6, "openat" );
+    //real_open = dlsym( libc6, "open" );
+    //real_fopen = dlsym( libc6, "fopen" );
     if ( ( data.tarmap = realpath( tarfile, 0 ) ) == 0 ) {
 	// Cannot find the tar file .. that's total badness!
 	perror( tarfile );