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bf2746b8ea
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 This PR also incorporates significantly changed model inference code (see the superceded PR https://github.com/Unidata/netcdf-c/pull/1259). 1.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.
57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
/* Copyright 2018-2018 University Corporation for Atmospheric
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Research/Unidata. */
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/**
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* Header file for dmode.c
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* @author Dennis Heimbigner
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*/
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#ifndef NCURLMODEL_H
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#define NCURLMODEL_H
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/* Define the io handler to be used to do lowest level
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access. This is above the libcurl level.
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Note that cases (DAP2,DAP4) where the implementation is 1-1
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with the iosp are not included.
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*/
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#define NC_IOSP_S3 (1)
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#define NC_IOSP_ZARR (1)
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/* Track the information from a URL that will help us
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infer how to access the data pointed to by that URL.
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*/
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typedef struct NCmode {
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int format; /* NC_FORMAT_XXX value */
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int implementation; /* NC_FORMATX_XXX value */
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int iosp; /* NC_IOSP_XXX value (above) */
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} NCmode;
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/* return 1 if path looks like a url; 0 otherwise */
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EXTERNL int NC_testurl(const char* path);
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/*
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Return an NC_FORMATX_... value.
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Assumes that the path is known to be a url.
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*/
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EXTERNL int NC_urlmodel(const char* path, int mode, char** newurl, NCmode* model);
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/**
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* Provide a hidden interface to allow utilities
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* to check if a given path name is really an ncdap3 url.
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* If no, put null in basenamep, else put basename of the url
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* minus any extension into basenamep; caller frees.
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* Return 1 if it looks like a url, 0 otherwise.
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*/
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EXTERNL int nc__testurl(const char* path, char** basenamep);
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/* allow access url parse and params without exposing nc_url.h */
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EXTERNL int NCDAP_urlparse(const char* s, void** dapurl);
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EXTERNL void NCDAP_urlfree(void* dapurl);
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EXTERNL const char* NCDAP_urllookup(void* dapurl, const char* param);
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/* Ping a specific server */
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EXTERNL int NCDAP2_ping(const char*);
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EXTERNL int NCDAP4_ping(const char*);
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#endif /*NCURLMODEL_H*/
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