[Mesa-dev] [wip 1/9] glsl: memory_writer helper class for data serialization

[Tapani Pälli]

On 01/13/2014 08:27 PM, Paul Berry wrote:
> On 2 January 2014 03:58, Tapani Pälli <tapani.palli at intel.com 
> <mailto:tapani.palli at intel.com>> wrote:
>
>     Class will be used by the shader binary cache implementation.
>
>     Signed-off-by: Tapani Pälli <tapani.palli at intel.com
>     <mailto:tapani.palli at intel.com>>
>     ---
>      src/glsl/memory_writer.h | 147
>     +++++++++++++++++++++++++++++++++++++++++++++++
>      1 file changed, 147 insertions(+)
>      create mode 100644 src/glsl/memory_writer.h
>
>     diff --git a/src/glsl/memory_writer.h b/src/glsl/memory_writer.h
>     new file mode 100644
>     index 0000000..a6c6b55
>     --- /dev/null
>     +++ b/src/glsl/memory_writer.h
>     @@ -0,0 +1,147 @@
>     +/* -*- c++ -*- */
>     +/*
>     + * Copyright © 2013 Intel Corporation
>     + *
>     + * Permission is hereby granted, free of charge, to any person
>     obtaining a
>     + * copy of this software and associated documentation files (the
>     "Software"),
>     + * to deal in the Software without restriction, including without
>     limitation
>     + * the rights to use, copy, modify, merge, publish, distribute,
>     sublicense,
>     + * and/or sell copies of the Software, and to permit persons to
>     whom the
>     + * Software is furnished to do so, subject to the following
>     conditions:
>     + *
>     + * The above copyright notice and this permission notice
>     (including the next
>     + * paragraph) shall be included in all copies or substantial
>     portions of the
>     + * Software.
>     + *
>     + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
>     KIND, EXPRESS OR
>     + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
>     MERCHANTABILITY,
>     + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO
>     EVENT SHALL
>     + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
>     DAMAGES OR OTHER
>     + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
>     OTHERWISE, ARISING
>     + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
>     OTHER
>     + * DEALINGS IN THE SOFTWARE.
>     + */
>     +
>     +#pragma once
>     +#ifndef MEMORY_WRITER_H
>     +#define MEMORY_WRITER_H
>     +
>     +#include <stdlib.h>
>     +#include <unistd.h>
>     +#include <string.h>
>     +
>     +#ifdef __cplusplus
>     +/**
>     + * Helper class for writing data to memory
>     + *
>     + * This class maintains a dynamically-sized memory buffer and allows
>     + * for data to be efficiently appended to it with automatic resizing.
>     + */
>     +class memory_writer
>     +{
>     +public:
>     +   memory_writer() :
>     +      memory(NULL),
>     +      curr_size(0),
>     +      pos(0) {}
>     +
>     +   ~memory_writer()
>     +   {
>     +      free(memory);
>     +   }
>     +
>     +   /* user wants to claim the memory */
>     +   char *release_memory(size_t *size)
>     +   {
>     +      /* final realloc to free allocated but unused memory */
>     +      char *result = (char *) realloc(memory, pos);
>     +      *size = pos;
>     +      memory = NULL;
>     +      curr_size = 0;
>     +      pos = 0;
>     +      return result;
>     +   }
>     +
>     +/**
>     + * write functions per type
>     + */
>     +#define DECL_WRITER(type) int write_ ##type (const type data) {\
>     +   return write(&data, sizeof(type));\
>     +}
>     +
>     +   DECL_WRITER(int32_t);
>     +   DECL_WRITER(int64_t);
>     +   DECL_WRITER(uint8_t);
>     +   DECL_WRITER(uint32_t);
>     +
>     +   int write_bool(bool data)
>     +   {
>     +      uint8_t val = data;
>     +      return write_uint8_t(val);
>     +   }
>     +
>     +   /* write function that reallocates more memory if required */
>     +   int write(const void *data, int32_t size)
>     +   {
>     +      if (!memory || pos > (int32_t)(curr_size - size))
>     +         if (grow(size))
>     +            return -1;
>     +
>     +      memcpy(memory + pos, data, size);
>     +
>     +      pos += size;
>     +      return 0;
>     +   }
>     +
>     +   int overwrite(const void *data, int32_t size, int32_t offset)
>     +   {
>     +      if (offset < 0 || offset + size > pos)
>     +         return -1;
>     +      memcpy(memory + offset, data, size);
>     +      return 0;
>     +   }
>     +
>     +   int write_string(const char *str)
>     +   {
>     +      if (!str)
>     +         return -1;
>     +      char terminator = '\0';
>     +      write(str, strlen(str));
>     +      write(&terminator, 1);
>
>
> C strings include a terminator, so there's no reason to write out the 
> string contents and the terminator separtely.  You can just do:
>
> write(str, strlen(str) + 1);
>
> Also, don't forget to propagate the return code to the caller:
>
> return write(str, strlen(str) + 1);

Ah right, will do. It could be that this needs to be modified back to 
how it was though (to write to length of the string too). I think it is 
otherwise impossible for the reader side to know if terminator really 
exists and it might continue to read forever (or call strlen for 
unterminated string).

>     +      return 0;
>     +   }
>     +
>     +   inline int32_t position() { return pos; }
>     +
>     +
>     +private:
>     +
>     +   /* reallocate more memory */
>     +   int grow(int32_t size)
>     +   {
>     +      int32_t new_size = 2 * (curr_size + size);
>     +      char *more_mem = (char *) realloc(memory, new_size);
>     +      if (more_mem == NULL) {
>     +         free(memory);
>     +         memory = NULL;
>     +         return -1;
>     +      } else {
>     +         memory = more_mem;
>     +         curr_size = new_size;
>     +         return 0;
>     +      }
>     +   }
>     +
>     +   /* allocated memory */
>     +   char *memory;
>     +
>     +   /* current size of the whole allocation */
>     +   int32_t curr_size;
>     +
>     +   /* write position / size of the data written */
>     +   int32_t pos;
>     +};
>     +
>     +#endif /* ifdef __cplusplus */
>     +
>     +#endif /* MEMORY_WRITER_H */
>     --
>     1.8.3.1
>
>

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