Add README and code generation scripts

.gitignore

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 deps/build.log
 deps/deps.jl
-gen
+gen/output
 Manifest.toml

README.md

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+CPLEXW.jl
+=========
+This package contains an unofficial low-level Julia wrapper for IBM® ILOG® CPLEX® Optimization Studio, automatically generated from the official C headers using [Clang.jl][1]. Unlike [CPLEX.jl][2], this wrapper allows access to all advanced CPLEX routines. However, it does not currently implement [MathOptInterface][3] or [MathProgBase][4] and therefore does not completely replace CPLEX.jl.
+
+**Disclaimer:** You cannot use CPLEXW.jl without having purchased and installed a copy of CPLEX Optimization Studio from IBM. This wrapper is maintained by the JuliaOpt community, and is **not** officially developed or supported by IBM.
+
+
+Installation
+------------
+Please follow the same install instructions from [CPLEX.jl][2], but instead of running `Pkg.add("CPLEX")`, run the following command instead:
+
+    Pkg.add("https://github.com/iSoron/CPLEXW.git")
+
+Usage
+-----
+
+The following example shows how can the package be used in standalone mode. After including `CPLEXW`, all standard CPLEX constants and functions (C API) become available to Julia. For a complete description of the available functions, please refer to the official CPLEX documentation. Julia's manual page on [how to call C functions][5] may also be helpful.
+
+    using CPLEXW
+
+    # Create CPLEX environment
+    rval = [Cint(0)]
+    env = CPXopenCPLEX(rval)
+
+    # Change some parameters
+    CPXsetintparam(env, CPX_PARAM_SCRIND, CPX_ON) # Print to the screen
+    CPXsetdblparam(env, CPX_PARAM_TILIM, 30)      # Time limit in seconds
+
+    # Create, populate and solve a problem
+    lp = CPXcreateprob(env, rval, "problem")
+    CPXreadcopyprob(env, lp, "myinstance.mps.gz", "mps")
+    CPXmipopt(env, lp)
+
+Usage with JuMP and CPLEX.jl
+----------------------------
+This package can also be used when you already have a JuMP optimization model (solved with CPLEX), but you need access to some advanced routines which are not available through CPLEX.jl. The next example illustrates this scenario:
+
+    using JuMP, CPLEX, CPLEXW
+
+    # Create JuMP + CPLEX.jl model
+    model = direct_model(CPLEX.Optimizer())
+    @variable(model, x >= 0)
+    @objective(model, Min, x)
+    optimize!(model)
+
+    # Call low-level CPLEX function
+    cpx = backend(model).inner
+    CPXgetnumnz(cpx.env, cpx.lp)
+
+Regenerating wrappers
+---------------------
+To regenerate the wrappers, run the script `gen/generate.jl`. The environment variable `CPLEX_INCLUDE_DIR` must be defined, and must point to the directory containing the header files. For example, if CPLEX is installed at `/opt/cplex-12.8`, the variable should be set to `/opt/cplex-12.8/cplex/include/ilcplex/`. If successful, the script will generate several files in the directory `gen/output`. Only the files `commons.jl` and `cplex.jl` are currently used.
+
+[1]: https://github.com/JuliaInterop/Clang.jl
+[2]: https://github.com/JuliaOpt/CPLEX.jl
+[3]: https://github.com/JuliaOpt/MathOptInterface.jl
+[4]: https://github.com/JuliaOpt/MathProgBase.jl
+[5]: https://docs.julialang.org/en/v1/manual/calling-c-and-fortran-code/

gen/generate.jl

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+using Clang
+
+if "CPLEX_INCLUDE_DIR" ∉ keys(ENV)
+    error("CPLEX_INCLUDE_DIR must be defined")
+end
+
+CPLEX_INCLUDE_DIR = ENV["CPLEX_INCLUDE_DIR"]
+
+mkpath("output")
+context = Clang.init(
+    headers=["$CPLEX_INCLUDE_DIR/cpxconst.h", "$CPLEX_INCLUDE_DIR/cplex.h"],
+    common_file="commons.jl",
+    output_dir="output",
+    clang_includes=vcat(CPLEX_INCLUDE_DIR, LLVM_INCLUDE),
+    clang_args = ["-I", CPLEX_INCLUDE_DIR],
+    clang_diagnostics=true,
+    header_wrapped=(header, cursorname) -> header == cursorname,
+    header_library=header_name -> "libcplex"
+)
+Clang.run(context)