Keep track of access mode to enforce API usage

3 files changed, 46 insertions, 5 deletions

diff --git a/src/microtar-stdio.c b/src/microtar-stdio.c
index e95b030..b022bf8 100644
--- a/src/microtar-stdio.c
+++ b/src/microtar-stdio.c
@@ -23,6 +23,7 @@
 
 #include "microtar.h"
 #include <stdio.h>
+#include <string.h>
 
 static int file_read(void* stream, void* data, unsigned size)
 {
@@ -57,10 +58,24 @@ static const mtar_ops_t file_ops = {
 
 int mtar_open(mtar_t* tar, const char* filename, const char* mode)
 {
+    /* Determine access mode */
+    int access;
+    char* read = strchr(mode, 'r');
+    char* write = strchr(mode, 'w');
+    if(read) {
+        if(write)
+            return MTAR_EAPI;
+        access = MTAR_READ;
+    } else if(write) {
+        access = MTAR_WRITE;
+    } else {
+        return MTAR_EAPI;
+    }
+
     /* Open file */
     FILE* file = fopen(filename, mode);
     if(!file)
         return MTAR_EOPENFAIL;
 
-    return mtar_init(tar, &file_ops, file);
+    return mtar_init(tar, access, &file_ops, file);
 }
diff --git a/src/microtar.c b/src/microtar.c
index e45f7bf..030bae9 100644
--- a/src/microtar.c
+++ b/src/microtar.c
@@ -291,9 +291,10 @@ const char* mtar_strerror(int err)
     }
 }
 
-int mtar_init(mtar_t* tar, const mtar_ops_t* ops, void* stream)
+int mtar_init(mtar_t* tar, int access, const mtar_ops_t* ops, void* stream)
 {
     memset(tar, 0, sizeof(mtar_t));
+    tar->access = access;
     tar->ops = ops;
     tar->stream = stream;
     return 0;
@@ -301,7 +302,7 @@ int mtar_init(mtar_t* tar, const mtar_ops_t* ops, void* stream)
 
 int mtar_close(mtar_t* tar)
 {
-    int err1 = mtar_finalize(tar);
+    int err1 = tar->access == MTAR_WRITE ? mtar_finalize(tar) : MTAR_ESUCCESS;
     int err2 = tar->ops->close(tar->stream);
 
     tar->ops = NULL;
@@ -328,6 +329,9 @@ const mtar_header_t* mtar_get_header(const mtar_t* tar)
 
 int mtar_rewind(mtar_t* tar)
 {
+    if(tar->access != MTAR_READ)
+        return MTAR_EAPI;
+
     int err = tseek(tar, 0);
     tar->state = 0;
     return err;
@@ -335,6 +339,9 @@ int mtar_rewind(mtar_t* tar)
 
 int mtar_next(mtar_t* tar)
 {
+    if(tar->access != MTAR_READ)
+        return MTAR_EAPI;
+
     if(tar->state & S_HEADER_VALID) {
         tar->state &= ~S_HEADER_VALID;
 
@@ -349,6 +356,9 @@ int mtar_next(mtar_t* tar)
 
 int mtar_foreach(mtar_t* tar, mtar_foreach_cb cb, void* arg)
 {
+    if(tar->access != MTAR_READ)
+        return MTAR_EAPI;
+
     int err = mtar_rewind(tar);
     if(err)
         return err;
@@ -383,6 +393,8 @@ int mtar_find(mtar_t* tar, const char* name)
 
 int mtar_read_data(mtar_t* tar, void* ptr, unsigned size)
 {
+    if(tar->access != MTAR_READ)
+        return MTAR_EAPI;
     if(!(tar->state & S_HEADER_VALID))
         return MTAR_EAPI;
 
@@ -405,6 +417,8 @@ int mtar_read_data(mtar_t* tar, void* ptr, unsigned size)
 
 int mtar_seek_data(mtar_t* tar, int offset, int whence)
 {
+    if(tar->access != MTAR_READ)
+        return MTAR_EAPI;
     if(!(tar->state & S_HEADER_VALID))
         return MTAR_EAPI;
 
@@ -444,7 +458,9 @@ int mtar_seek_data(mtar_t* tar, int offset, int whence)
 
 int mtar_eof_data(mtar_t* tar)
 {
-    /* API usage error, but just claim EOF. */
+    /* API usage errors, but just claim EOF. */
+    if(tar->access != MTAR_READ)
+        return 1;
     if(!(tar->state & S_HEADER_VALID))
         return 1;
 
@@ -453,6 +469,8 @@ int mtar_eof_data(mtar_t* tar)
 
 int mtar_write_header(mtar_t* tar, const mtar_header_t* h)
 {
+    if(tar->access != MTAR_WRITE)
+        return MTAR_EAPI;
     if(tar->state & S_WROTE_FINALIZE)
         return MTAR_EAPI;
 
@@ -538,6 +556,8 @@ int mtar_write_data(mtar_t* tar, const void* ptr, unsigned size)
 
 int mtar_finalize(mtar_t* tar)
 {
+    if(tar->access != MTAR_WRITE)
+        return MTAR_EAPI;
     if(tar->state & S_WROTE_FINALIZE)
         return MTAR_ESUCCESS;
 
diff --git a/src/microtar.h b/src/microtar.h
index d2e472b..d42bda6 100644
--- a/src/microtar.h
+++ b/src/microtar.h
@@ -58,6 +58,11 @@ enum {
     MTAR_TFIFO  = '6',
 };
 
+enum {
+    MTAR_READ,
+    MTAR_WRITE,
+};
+
 typedef struct mtar_header mtar_header_t;
 typedef struct mtar mtar_t;
 typedef struct mtar_ops mtar_ops_t;
@@ -86,6 +91,7 @@ struct mtar {
     char buffer[512];       /* IO buffer, put first to allow library users to
                              * control its alignment */
     int state;              /* Used to simplify the API and verify API usage */
+    int access;             /* Access mode */
     unsigned pos;           /* Current position in file */
     unsigned header_pos;    /* Position of the current header */
     mtar_header_t header;   /* Most recently parsed header */
@@ -97,7 +103,7 @@ const char* mtar_strerror(int err);
 
 int mtar_open(mtar_t* tar, const char* filename, const char* mode);
 
-int mtar_init(mtar_t* tar, const mtar_ops_t* ops, void* stream);
+int mtar_init(mtar_t* tar, int access, const mtar_ops_t* ops, void* stream);
 int mtar_close(mtar_t* tar);
 int mtar_is_open(mtar_t* tar);