Merge RFC4 (#1865)

This commit is the result of the squashing of rfc4_dev branch in a single
commit. It implements mostly RFC 4 related work.

* Grid handling:
  - remove obsolete and presumably unfinished implementation of grid catalog functionality
  - all grid functionality is in grids.cpp/.hpp
  - vertical and horizontal grid shift: rework to no longer load whole grid into memory
  - remove hgrids and vgrids member from PJ structure, and store them in hgridshift/vgridshift/deformation structures
  - build systems: add optional libtiff dependency. Must be explicitly disabled if not desired
  - add support for horizontal and vertical grids in GeoTIFF, if libtiff is available
  - add GenericShiftGridSet and GenericShiftGrid classes, relying on TIFF grids, that can be used for generic purpose grid-based adjustment
  - add a +proj=xyzgridshift method to perform geocentric translation by grid. Used for French NTF to RGF93 transformation using gr3df97a.tif grid
  - deformation: add support for +grids= for GeoTIFF grids
  - horizontal grid shift: fix failures on points slightly outside a subgrid (fixes #209)

* File management:
  - add a filemanager.cpp/.hpp to deal with file related work
  - test for legacy proj_api.h fileapi
  - proj.h: add proj_context_set_fileapi() and proj_context_set_sqlite3_vfs_name() (fixes #866)
  - add capability to read resource files from the user writable directory

* Network access:
  - build systems: add optional curl dependency
  - add a curl-based default implementation for network related functionality
  - proj.h: add C API to control network functionality, and optionaly provide network callbacks
  - add data/proj.ini with default settings
  - add a SQLite3 local cache of downloaded chunks
  - add proj_is_download_needed() and proj_download_file()

* Use Win32 Unicode APIs and expect all strings to be UTF-8 (fixes #1765)
  For backward compatibility, if PROJ_LIB content is found to be not UTF-8 or
  pointing to a non existing directory, then an attempt at interpretating it
  in the ANSI page encoding is done.
  proj_context_set_search_paths() now assumes strings to be in UTF-8, and
  functions returning paths will also return values in UTF-8.

1 files changed, 31 insertions, 5 deletions

diff --git a/src/fileapi.cpp b/src/fileapi.cpp
index 70c7b5de..70be2502 100644
--- a/src/fileapi.cpp
+++ b/src/fileapi.cpp
@@ -34,6 +34,7 @@
 
 #include "proj.h"
 #include "proj_internal.h"
+#include "filemanager.hpp"
 
 static PAFile stdio_fopen(projCtx ctx, const char *filename,
                              const char *access);
@@ -141,7 +142,7 @@ static void stdio_fclose(PAFile file)
 
 PAFile pj_ctx_fopen(projCtx ctx, const char *filename, const char *access)
 {
-    return ctx->fileapi->FOpen(ctx, filename, access);
+    return ctx->fileapi_legacy->FOpen(ctx, filename, access);
 }
 
 /************************************************************************/
@@ -149,7 +150,7 @@ PAFile pj_ctx_fopen(projCtx ctx, const char *filename, const char *access)
 /************************************************************************/
 size_t pj_ctx_fread(projCtx ctx, void *buffer, size_t size, size_t nmemb, PAFile file)
 {
-    return ctx->fileapi->FRead(buffer, size, nmemb, file);
+    return ctx->fileapi_legacy->FRead(buffer, size, nmemb, file);
 }
 
 /************************************************************************/
@@ -157,7 +158,7 @@ size_t pj_ctx_fread(projCtx ctx, void *buffer, size_t size, size_t nmemb, PAFile
 /************************************************************************/
 int    pj_ctx_fseek(projCtx ctx, PAFile file, long offset, int whence)
 {
-    return ctx->fileapi->FSeek(file, offset, whence);
+    return ctx->fileapi_legacy->FSeek(file, offset, whence);
 }
 
 /************************************************************************/
@@ -165,7 +166,7 @@ int    pj_ctx_fseek(projCtx ctx, PAFile file, long offset, int whence)
 /************************************************************************/
 long   pj_ctx_ftell(projCtx ctx, PAFile file)
 {
-    return ctx->fileapi->FTell(file);
+    return ctx->fileapi_legacy->FTell(file);
 }
 
 /************************************************************************/
@@ -173,7 +174,7 @@ long   pj_ctx_ftell(projCtx ctx, PAFile file)
 /************************************************************************/
 void   pj_ctx_fclose(projCtx ctx, PAFile file)
 {
-    ctx->fileapi->FClose(file);
+    ctx->fileapi_legacy->FClose(file);
 }
 
 /************************************************************************/
@@ -212,3 +213,28 @@ char *pj_ctx_fgets(projCtx ctx, char *line, int size, PAFile file)
     }
     return line;
 }
+
+/************************************************************************/
+/*                         pj_ctx_set_fileapi()                         */
+/************************************************************************/
+
+void pj_ctx_set_fileapi( projCtx ctx, projFileAPI *fileapi )
+
+{
+    if (nullptr==ctx)
+        return;
+    ctx->fileapi_legacy = fileapi;
+}
+
+/************************************************************************/
+/*                         pj_ctx_get_fileapi()                         */
+/************************************************************************/
+
+projFileAPI *pj_ctx_get_fileapi( projCtx ctx )
+
+{
+    if (nullptr==ctx)
+        return nullptr;
+    return ctx->fileapi_legacy;
+}
+