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netcdf-c/include/ncmodel.h

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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 This PR also incorporates significantly changed model inference code (see the superceded PR https://github.com/Unidata/netcdf-c/pull/1259). 1.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.
2019-01-02 09:27:36 +08:00
/* Copyright 2018-2018 University Corporation for Atmospheric
Research/Unidata. */
/**
* Functions for inferring dataset model
* @author Dennis Heimbigner
*/
#ifndef NCINFERMODEL_H
#define NCINFERMODEL_H
/* Track the information hat will help us
infer how to access the data defined by
Change (again), and hopefully simplify, the file model inference algorithm. * For URL paths, the new approach essentially centralizes all information in the URL into the "#mode=" fragment key and uses that value to determine the dispatcher for (most) URLs. * The new approach has the following steps: 1. canonicalize the path if it is a URL. 2. use the mode= fragment key to determine the dispatcher 3. if dispatcher still not determined, then use the mode flags argument to nc_open/nc_create to determine the dispatcher. 4. if the path points to something readable, attempt to read the magic number at the front, and use that to determine the dispatcher. this case may override all previous cases. * Misc changes. 1. Update documentation 2. Moved some unit tests from libdispatch to unit_test directory. 3. Fixed use of wrong #ifdef macro in test_filter_reg.c [I think this may fix an previously reported esupport query].
2019-09-30 02:59:28 +08:00
path + omode + (sometimes) file content.
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.
2019-01-02 09:27:36 +08:00
*/
typedef struct NCmodel {
int impl; /* NC_FORMATX_XXX value */
Change (again), and hopefully simplify, the file model inference algorithm. * For URL paths, the new approach essentially centralizes all information in the URL into the "#mode=" fragment key and uses that value to determine the dispatcher for (most) URLs. * The new approach has the following steps: 1. canonicalize the path if it is a URL. 2. use the mode= fragment key to determine the dispatcher 3. if dispatcher still not determined, then use the mode flags argument to nc_open/nc_create to determine the dispatcher. 4. if the path points to something readable, attempt to read the magic number at the front, and use that to determine the dispatcher. this case may override all previous cases. * Misc changes. 1. Update documentation 2. Moved some unit tests from libdispatch to unit_test directory. 3. Fixed use of wrong #ifdef macro in test_filter_reg.c [I think this may fix an previously reported esupport query].
2019-09-30 02:59:28 +08:00
int format; /* NC_FORMAT_XXX value; Used to remember extra info; */
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.
2019-01-02 09:27:36 +08:00
} NCmodel;
/* Keep compiler quiet */
struct NCURI;
struct NC_dispatch;
Change (again), and hopefully simplify, the file model inference algorithm. * For URL paths, the new approach essentially centralizes all information in the URL into the "#mode=" fragment key and uses that value to determine the dispatcher for (most) URLs. * The new approach has the following steps: 1. canonicalize the path if it is a URL. 2. use the mode= fragment key to determine the dispatcher 3. if dispatcher still not determined, then use the mode flags argument to nc_open/nc_create to determine the dispatcher. 4. if the path points to something readable, attempt to read the magic number at the front, and use that to determine the dispatcher. this case may override all previous cases. * Misc changes. 1. Update documentation 2. Moved some unit tests from libdispatch to unit_test directory. 3. Fixed use of wrong #ifdef macro in test_filter_reg.c [I think this may fix an previously reported esupport query].
2019-09-30 02:59:28 +08:00
/* Infer model implementation */
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.
2019-01-02 09:27:36 +08:00
EXTERNL int NC_infermodel(const char* path, int* omodep, int iscreate, int useparallel, void* params, NCmodel* model, char** newpathp);
/**
* Provide a hidden interface to allow utilities
* to check if a given path name is really a url.
* If not, put null in basenamep, else put basename of the url
* minus any extension into basenamep; caller frees.
* Return 1 if it looks like a url, 0 otherwise.
*/
EXTERNL int nc__testurl(const char* path, char** basenamep);
#endif /*NCINFERMODEL_H*/
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