Merge pull request #631 from achaikou/expose_datasources_to_python_bindings

Expose datasources to python bindings

Author: achaikou

lib/include/segyio/segy.h

@@ -139,6 +139,8 @@ typedef struct {
 
 segy_file* segy_open( const char* path, const char* mode );
 int segy_mmap( segy_datasource* );
+segy_datasource* segy_memopen( unsigned char* addr, size_t size );
+
 int segy_flush( segy_datasource* );
 int segy_close( segy_datasource* );
 
@@ -774,6 +776,8 @@ typedef enum {
     SEGY_READONLY,
     SEGY_NOTFOUND,
     SEGY_MEMORY_ERROR,
+    SEGY_DS_FLUSH_ERROR,
+    SEGY_DS_CLOSE_ERROR,
     // values are duplicated until enum is properly cleaned
     SEGY_DS_READ_ERROR = SEGY_FREAD_ERROR,
     SEGY_DS_WRITE_ERROR = SEGY_FWRITE_ERROR,

lib/src/segy.c

@@ -565,6 +565,11 @@ static int mmapflush( segy_datasource* self ) {
     return SEGY_OK;
 }
 
+static int memflush( segy_datasource* self ) {
+    (void)self; // mark parameter as unused
+    return SEGY_OK;
+}
+
 static int mmapclose( segy_datasource* self ) {
 #ifdef HAVE_MMAP
     int err = mmapflush( self );
@@ -578,6 +583,12 @@ static int mmapclose( segy_datasource* self ) {
     return SEGY_OK;
 }
 
+static int memclose( segy_datasource* self ) {
+    memfile* mp = (memfile*)self->stream;
+    free( mp );
+    return SEGY_OK;
+}
+
 static int formatsize( int format ) {
     switch( format ) {
         case SEGY_IBM_FLOAT_4_BYTE:             return 4;
@@ -676,6 +687,47 @@ segy_file* segy_open( const char* path, const char* mode ) {
     return ds;
 }
 
+segy_datasource* segy_memopen( unsigned char* addr, size_t size ) {
+    if( !addr || !size ) return NULL;
+
+    /* as we don't support operations that change file size on update, no memory
+     * resize would be needed
+     */
+    memfile* mp = malloc( sizeof( memfile ) );
+    if( !mp ) {
+        return NULL;
+    }
+    mp->addr = addr;
+    mp->cur = addr;
+    mp->size = size;
+
+    segy_datasource* ds = malloc( sizeof( segy_datasource ) );
+    if( !ds ) {
+        free( mp );
+        return NULL;
+    }
+    ds->stream = mp;
+
+    ds->read = memread;
+    ds->write = memwrite;
+    ds->seek = memseek;
+    ds->tell = memtell;
+    ds->size = memsize;
+    ds->flush = memflush;
+    ds->close = memclose;
+
+    ds->writable = true;
+
+    // on init assume a size of 4-bytes-per-element and big-endian
+    ds->elemsize = 4;
+    ds->lsb = false;
+
+    ds->minimize_requests_number = false;
+    ds->memory_speedup = true;
+
+    return ds;
+}
+
 int segy_mmap( segy_datasource* ds ) {
 #ifndef HAVE_MMAP
     return SEGY_MMAP_INVALID;
@@ -735,7 +787,7 @@ int segy_flush( segy_datasource* ds ) {
     if( !ds->writable ) return SEGY_OK;
 
     int flusherr = ds->flush( ds );
-    if( flusherr != 0 ) return SEGY_DS_ERROR;
+    if( flusherr != 0 ) return SEGY_DS_FLUSH_ERROR;
 
     return SEGY_OK;
 }
@@ -759,7 +811,7 @@ int segy_close( segy_datasource* ds ) {
 
     err = ds->close(ds);
     free( ds );
-    if( err != 0 ) return SEGY_DS_ERROR;
+    if( err != 0 ) return SEGY_DS_CLOSE_ERROR;
     return SEGY_OK;
 }
 

python/segyio/create.py

@@ -193,8 +193,9 @@ def create(filename, spec):
     if endian is None:
         endian = 'big'
 
-
-    fd = _segyio.segyfd(str(filename), 'w+', c_endianness(endian))
+    fd = _segyio.segyfd(
+        filename=str(filename), mode='w+', endianness=c_endianness(endian)
+    )
     fd.segymake(
         samples = len(samples),
         tracecount = tracecount,

python/segyio/open.py

@@ -149,7 +149,9 @@ def open(filename, mode="r", iline = 189,
         raise ValueError(', '.join((problem, solution)))
 
     from . import _segyio
-    fd = _segyio.segyfd(str(filename), mode, c_endianness(endian))
+    fd = _segyio.segyfd(
+        filename=str(filename), mode=mode, endianness=c_endianness(endian)
+    )
     fd.segyopen()
     metrics = fd.metrics()