netcdf-c/libhdf5/H5FDhttp.h
Dennis Heimbigner bf2746b8ea Provide byte-range reading of remote datasets
re: issue https://github.com/Unidata/netcdf-c/issues/1251

Assume that you have the URL to a remote dataset
which is a normal netcdf-3 or netcdf-4 file.

This PR allows the netcdf-c to read that dataset's
contents as a netcdf file using HTTP byte ranges
if the remote server supports byte-range access.

Originally, this PR was set up to access Amazon S3 objects,
but it can also access other remote datasets such as those
provided by a Thredds server via the HTTPServer access protocol.
It may also work for other kinds of servers.

Note that this is not intended as a true production
capability because, as is known, this kind of access to
can be quite slow. In addition, the byte-range IO drivers
do not currently do any sort of optimization or caching.

An additional goal here is to gain some experience with
the Amazon S3 REST protocol.

This architecture and its use documented in
the file docs/byterange.dox.

There are currently two test cases:

1. nc_test/tst_s3raw.c - this does a simple open, check format, close cycle
   for a remote netcdf-3 file and a remote netcdf-4 file.
2. nc_test/test_s3raw.sh - this uses ncdump to investigate some remote
   datasets.

This PR also incorporates significantly changed model inference code
(see the superceded PR https://github.com/Unidata/netcdf-c/pull/1259).

1. It centralizes the code that infers the dispatcher.
2. It adds support for byte-range URLs

Other changes:

1. NC_HDF5_finalize was not being properly called by nc_finalize().
2. Fix minor bug in ncgen3.l
3. fix memory leak in nc4info.c
4. add code to walk the .daprc triples and to replace protocol=
   fragment tag with a more general mode= tag.

Final Note:
Th inference code is still way too complicated. We need to move
to the validfile() model used by netcdf Java, where each
dispatcher is asked if it can process the file. This decentralizes
the inference code. This will be done after all the major new
dispatchers (PIO, Zarr, etc) have been implemented.
2019-01-01 18:27:36 -07:00

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C

/*********************************************************************
* Copyright 2018, UCAR/Unidata
* See netcdf/COPYRIGHT file for copying and redistribution conditions.
* ********************************************************************/
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Copyright by The HDF Group. *
* Copyright by the Board of Trustees of the University of Illinois. *
* All rights reserved. *
* *
* This file is part of HDF5. The full HDF5 copyright notice, including *
* terms governing use, modification, and redistribution, is contained in *
* the COPYING file, which can be found at the root of the source code *
* distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases. *
* If you do not have access to either file, you may request a copy from *
* help@hdfgroup.org. *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*
* Programmer: Dennis Heimbigner (dmh@ucar.edu)
* Dec. 26 2018
*
* Purpose: The public header file for the s3 driver.
*
* Derived from the HDF5 Source file H5FDstdio.c
*/
#ifndef H5FDHTTP_H
#define H5FDHTTP_H
#include "H5Ipublic.h"
#define H5FD_HTTP (H5FD_http_init())
#ifdef __cplusplus
extern "C" {
#endif
#if 0
H5_DLL hid_t H5FD_http_init(void);
H5_DLL herr_t H5Pset_fapl_http(hid_t fapl_id);
#else
EXTERNL hid_t H5FD_http_init(void);
EXTERNL herr_t H5Pset_fapl_http(hid_t fapl_id);
#endif
#ifdef __cplusplus
}
#endif
#endif /*H5FDHTTP_H*/