--- /dev/null
+
+/* pngrio.c - functions for data input
+ *
+ * Last changed in libpng 1.5.0 [January 6, 2011]
+ * Copyright (c) 1998-2011 Glenn Randers-Pehrson
+ * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
+ * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ *
+ * This file provides a location for all input. Users who need
+ * special handling are expected to write a function that has the same
+ * arguments as this and performs a similar function, but that possibly
+ * has a different input method. Note that you shouldn't change this
+ * function, but rather write a replacement function and then make
+ * libpng use it at run time with png_set_read_fn(...).
+ */
+
+#include "pngpriv.h"
+
+#ifdef PNG_READ_SUPPORTED
+
+/* Read the data from whatever input you are using. The default routine
+ * reads from a file pointer. Note that this routine sometimes gets called
+ * with very small lengths, so you should implement some kind of simple
+ * buffering if you are using unbuffered reads. This should never be asked
+ * to read more then 64K on a 16 bit machine.
+ */
+void /* PRIVATE */
+png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
+{
+ png_debug1(4, "reading %d bytes", (int)length);
+
+ if (png_ptr->read_data_fn != NULL)
+ (*(png_ptr->read_data_fn))(png_ptr, data, length);
+
+ else
+ png_error(png_ptr, "Call to NULL read function");
+}
+
+#ifdef PNG_STDIO_SUPPORTED
+/* This is the function that does the actual reading of data. If you are
+ * not reading from a standard C stream, you should create a replacement
+ * read_data function and use it at run time with png_set_read_fn(), rather
+ * than changing the library.
+ */
+# ifndef USE_FAR_KEYWORD
+void PNGCBAPI
+png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
+{
+ png_size_t check;
+
+ if (png_ptr == NULL)
+ return;
+
+ /* fread() returns 0 on error, so it is OK to store this in a png_size_t
+ * instead of an int, which is what fread() actually returns.
+ */
+ check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr);
+
+ if (check != length)
+ png_error(png_ptr, "Read Error");
+}
+# else
+/* This is the model-independent version. Since the standard I/O library
+ can't handle far buffers in the medium and small models, we have to copy
+ the data.
+*/
+
+#define NEAR_BUF_SIZE 1024
+#define MIN(a,b) (a <= b ? a : b)
+
+static void PNGCBAPI
+png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
+{
+ png_size_t check;
+ png_byte *n_data;
+ png_FILE_p io_ptr;
+
+ if (png_ptr == NULL)
+ return;
+
+ /* Check if data really is near. If so, use usual code. */
+ n_data = (png_byte *)CVT_PTR_NOCHECK(data);
+ io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
+
+ if ((png_bytep)n_data == data)
+ {
+ check = fread(n_data, 1, length, io_ptr);
+ }
+
+ else
+ {
+ png_byte buf[NEAR_BUF_SIZE];
+ png_size_t read, remaining, err;
+ check = 0;
+ remaining = length;
+
+ do
+ {
+ read = MIN(NEAR_BUF_SIZE, remaining);
+ err = fread(buf, 1, read, io_ptr);
+ png_memcpy(data, buf, read); /* copy far buffer to near buffer */
+
+ if (err != read)
+ break;
+
+ else
+ check += err;
+
+ data += read;
+ remaining -= read;
+ }
+ while (remaining != 0);
+ }
+
+ if ((png_uint_32)check != (png_uint_32)length)
+ png_error(png_ptr, "read Error");
+}
+# endif
+#endif
+
+/* This function allows the application to supply a new input function
+ * for libpng if standard C streams aren't being used.
+ *
+ * This function takes as its arguments:
+ *
+ * png_ptr - pointer to a png input data structure
+ *
+ * io_ptr - pointer to user supplied structure containing info about
+ * the input functions. May be NULL.
+ *
+ * read_data_fn - pointer to a new input function that takes as its
+ * arguments a pointer to a png_struct, a pointer to
+ * a location where input data can be stored, and a 32-bit
+ * unsigned int that is the number of bytes to be read.
+ * To exit and output any fatal error messages the new write
+ * function should call png_error(png_ptr, "Error msg").
+ * May be NULL, in which case libpng's default function will
+ * be used.
+ */
+void PNGAPI
+png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
+ png_rw_ptr read_data_fn)
+{
+ if (png_ptr == NULL)
+ return;
+
+ png_ptr->io_ptr = io_ptr;
+
+#ifdef PNG_STDIO_SUPPORTED
+ if (read_data_fn != NULL)
+ png_ptr->read_data_fn = read_data_fn;
+
+ else
+ png_ptr->read_data_fn = png_default_read_data;
+#else
+ png_ptr->read_data_fn = read_data_fn;
+#endif
+
+ /* It is an error to write to a read device */
+ if (png_ptr->write_data_fn != NULL)
+ {
+ png_ptr->write_data_fn = NULL;
+ png_warning(png_ptr,
+ "Can't set both read_data_fn and write_data_fn in the"
+ " same structure");
+ }
+
+#ifdef PNG_WRITE_FLUSH_SUPPORTED
+ png_ptr->output_flush_fn = NULL;
+#endif
+}
+#endif /* PNG_READ_SUPPORTED */
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