Re: Converting void* to D array
On 4/15/15 8:35 AM, CraigDillabaugh wrote: On Wednesday, 15 April 2015 at 11:18:03 UTC, Steven Schveighoffer wrote: immutable blocksize = GByte.sizeof * x_block_size * y_block_size; auto buffer = malloc(blocksize)[0..blocksize]; Also, you don't need to cast pointers to void *. Should be able to do: GDALReadBlock(AGDALRasterBandHInstance, xblock, yblock, buffer.ptr); Thanks for the pointers (no pun intended!) Just out of curiosity, what is the type of 'buffer'? 'malloc' returns a void* but using the .ptr suggests 'buffer' is an array. Is the return of malloc automatically converted to an array? malloc returns void *, but I am applying the slice operator which turns a pointer into a slice. I'll split it up: auto bufptr = malloc(blocksize);// typeof(bufptr) = void * auto buffer = bufptr[0..blocksize]; // typeof(buffer) = void[] -Steve
Re: Converting void* to D array
On Wednesday, 15 April 2015 at 11:18:03 UTC, Steven Schveighoffer wrote: On 4/15/15 12:47 AM, Daniel Kozak wrote: On Wednesday, 15 April 2015 at 04:43:39 UTC, Daniel Kozák wrote: On Wed, 15 Apr 2015 04:24:20 + Craig Dillabaugh via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer? Or you probably can do it like this: auto buffer = new GByte[xblock*yblock]; GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, (cast void*)buffer.ptr ); But in this case memory will be scan by GC. Which probably is not something what you want. Depends on what GByte is. If it doesn't contain pointers (I'm assuming its probably ubyte?), then it won't be scanned. If you still want to use malloc, but in a safe way, you can do: immutable blocksize = GByte.sizeof * x_block_size * y_block_size; auto buffer = malloc(blocksize)[0..blocksize]; Also, you don't need to cast pointers to void *. Should be able to do: GDALReadBlock(AGDALRasterBandHInstance, xblock, yblock, buffer.ptr); -Steve Thanks for the pointers (no pun intended!) Just out of curiosity, what is the type of 'buffer'? 'malloc' returns a void* but using the .ptr suggests 'buffer' is an array. Is the return of malloc automatically converted to an array?
Re: Converting void* to D array
On Wednesday, 15 April 2015 at 11:18:03 UTC, Steven Schveighoffer wrote: clip Depends on what GByte is. If it doesn't contain pointers (I'm assuming its probably ubyte?), then it won't be scanned. clip -Steve Yes, GByte is an alias for ubyte.
Re: Converting void* to D array
On Wednesday, 15 April 2015 at 14:02:38 UTC, Steven Schveighoffer wrote: On 4/15/15 8:35 AM, CraigDillabaugh wrote: On Wednesday, 15 April 2015 at 11:18:03 UTC, Steven Schveighoffer wrote: immutable blocksize = GByte.sizeof * x_block_size * y_block_size; auto buffer = malloc(blocksize)[0..blocksize]; Also, you don't need to cast pointers to void *. Should be able to do: GDALReadBlock(AGDALRasterBandHInstance, xblock, yblock, buffer.ptr); Thanks for the pointers (no pun intended!) Just out of curiosity, what is the type of 'buffer'? 'malloc' returns a void* but using the .ptr suggests 'buffer' is an array. Is the return of malloc automatically converted to an array? malloc returns void *, but I am applying the slice operator which turns a pointer into a slice. I'll split it up: auto bufptr = malloc(blocksize);// typeof(bufptr) = void * auto buffer = bufptr[0..blocksize]; // typeof(buffer) = void[] -Steve Nice. Thanks. I didn't realize you can slice a bare pointer like that. Does druntime have any way of making sure that is safe, or are you on your own?
Re: Converting void* to D array
On 4/15/15 11:02 AM, CraigDillabaugh wrote: Nice. Thanks. I didn't realize you can slice a bare pointer like that. Does druntime have any way of making sure that is safe, or are you on your own? No, druntime cannot know what the pointer actually points at. This would not work in @safe code. It's on you to make sure it's valid. -Steve
Re: Converting void* to D array
On 4/15/15 12:47 AM, Daniel Kozak wrote: On Wednesday, 15 April 2015 at 04:43:39 UTC, Daniel Kozák wrote: On Wed, 15 Apr 2015 04:24:20 + Craig Dillabaugh via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer? Or you probably can do it like this: auto buffer = new GByte[xblock*yblock]; GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, (cast void*)buffer.ptr ); But in this case memory will be scan by GC. Which probably is not something what you want. Depends on what GByte is. If it doesn't contain pointers (I'm assuming its probably ubyte?), then it won't be scanned. If you still want to use malloc, but in a safe way, you can do: immutable blocksize = GByte.sizeof * x_block_size * y_block_size; auto buffer = malloc(blocksize)[0..blocksize]; Also, you don't need to cast pointers to void *. Should be able to do: GDALReadBlock(AGDALRasterBandHInstance, xblock, yblock, buffer.ptr); -Steve
Re: Converting void* to D array
On Wednesday, 15 April 2015 at 04:43:39 UTC, Daniel Kozák wrote: On Wed, 15 Apr 2015 04:24:20 + Craig Dillabaugh via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer? Or you probably can do it like this: auto buffer = new GByte[xblock*yblock]; GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, (cast void*)buffer.ptr ); But in this case memory will be scan by GC. Which probably is not something what you want.
Re: Converting void* to D array
On Wed, 15 Apr 2015 04:24:20 + Craig Dillabaugh via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer? Or you probably can do it like this: auto buffer = new GByte[xblock*yblock]; GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, (cast void*)buffer.ptr );
Re: Converting void* to D array
On Wednesday, 15 April 2015 at 04:43:39 UTC, Daniel Kozák wrote: On Wed, 15 Apr 2015 04:24:20 + Craig Dillabaugh via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer? Or you probably can do it like this: auto buffer = new GByte[xblock*yblock]; GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, (cast void*)buffer.ptr ); Thank you very much. Works like a charm. Make that last line: GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, cast(void*)buffer.ptr );
Converting void* to D array
Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer?
Re: Converting void* to D array
On Wed, 15 Apr 2015 04:24:20 + Craig Dillabaugh via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Hi. I want to call a C library function that returns a data buffer as a void*. How do I convert the resulting void* into something I can process in D? //I have the following function from the GDAL C library. extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, void* ); So I have (GByte is defined in the GDAL library): void* buffer = malloc( GByte.sizeof * x_block_size * y_block_size ); I fill the buffer (and ignore any errors :o) GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, buffer ); Now, how can I access the data in buffer? auto buf = (cast(GByte *)buffer)[0 .. xblock * yblock];
